unit 6 uses of electromagnetic waves

Unit 6

Uses of Electromagnetic Waves

Table of Contents Table of Contents 1

Introduction 3

Essential Questions 4

Review 4

Lesson 6.1: Uses of Electromagnetic Waves in Nature 5 Objectives 5 Warm-Up 5 Learn about It 7 Key Points 10 Web Links 11 Check Your Understanding 11 Challenge Yourself 12

Lesson 6.2: Technological Applications of Electromagnetic Waves 13 Objectives 13 Warm-Up 13 Learn about It 14 Key Points 19 Web Links 19 Check Your Understanding 20 Challenge Yourself 20

Lesson 6.3: Applications of Electromagnetic Waves in Sanitation and Health 21 Objectives 21 Warm-Up 21 Learn about It 22 Key Points 25 Web Links 25 Check Your Understanding 26

https://docs.google.com/document/d/1dWLz5aTsWcTaEYjNPSfoP50Kk-9zHzwKvtIsNRItMRg/edit#heading=h.9lz4sycbwaag

Challenge Yourself 27

Lesson 6.4: Hazards of Electromagnetic Waves 28 Objectives 28 Warm-Up 28 Learn about It 29 Key Points 31 Web Links 31 Check Your Understanding 32 Challenge Yourself 33

Laboratory Activity 34

Performance Task 36

Self Check 37

Key Words 38

Wrap Up 39

Photo Credits 39

References 41

Copyright © 2018 Quipper Limited 2

GRADE 10 | SCIENCE

Unit 6 Uses of Electromagnetic Waves

From telecommunications to the field of medicine, electromagnetic waves have various functions in the our society as well as in the ecosystem. Scientists, inventors and engineers are amazed with the promising characteristics the waves in the spectrum which led them to continue several innovations in technology. An example of this enhanced and innovated technology using the electromagnetic wave is the Advanced Extremely High Frequency (AEHF) satellite which is developed to be used to relay secured information in military communication. Electromagnetic waves are able to travel in vacuum, hence, its ability to travel outside Earth. In this unit, the uses of the electromagnetic waves in nature, technology, sanitation, and health will be tackled. This will give you a perspective of how these waves carry a promising future with its propagation since the history of its discovery.


Essential Questions

At the end of this unit, you should be able to answer the following questions.

● How are electromagnetic waves used in nature? ● How are the different uses of certain parts of the electromagnetic spectrum

used in technological applications? ● What are the practical applications of electromagnetic waves and how does it

contribute to the improvement of the field of medicine? ● What are the hazards in using or being exposed in some electromagnetic

waves?

Review

● Electromagnetic waves are waves that are made of electric and magnetic field components. They do not need a medium to propagate, hence, they can travel through space.

● Light, as well as EM waves, exhibits different behaviors when it encounters a medium. Some of the behaviors of light discussed previously were reflection, refraction, dispersion, absorption, interference, diffraction, transmission, and scattering.

● The speed at which a wave propagates is given by the following equation:

where v is the speed of the wave is m/s, is its wavelength in m, while f is itsλ frequency in Hz.

● In an electromagnetic spectrum, the types of waves are arranged in increasing frequency resulting from a decrease wavelength. This trend will result to an increase in energy being carried by the wave.

● The electromagnetic spectrum is composed of the following types of waves in increasing frequency: radio wave, microwave, infrared, visible light, ultraviolet wave, X-ray, and gamma ray.


Lesson 6.1: Uses of Electromagnetic Waves in Nature

Objectives In this lesson, you should be able to:

● enumerate some uses of electromagnetic waves in nature; and ● show how electromagnetic waves are used in nature.

Nature shows many ways on how different organisms use electromagnetic waves in their daily routine. These uses range from simple communication between species to complex signal transmission within an organism. How are EM waves utilized by organisms in nature?

Warm-Up

Glowing Chemicals Part A: Chemiluminescence in the Lab Materials:

● 1 g luminol ● 50 ml sodium hydroxide 10% w/w solution ● 50 ml potassium ferricyanide 3% w/w solution ● approximately 0.5 g potassium ferricyanide ● 3 ml hydrogen peroxide 30% m/m solution ● distilled water ● beakers ● funnel ● cylinders ● flask

Procedure:

1. Wear your laboratory gown and goggles or gloves if needed. 2. In a beaker, dissolve 1 g luminol in 450 ml distilled water. 3. Add 50 mL 10% sodium hydroxide solution and mix.


4. Take 50 mL of the resulting solution and add it to 350 mL distilled water in another beaker. This is now Solution A.

5. In a third beaker, mix 50 mL 3% potassium ferricyanide solution with 350 mL distilled water and 3 ml 30% hydrogen peroxide solution. This is Solution B.

6. Pour equal amounts of Solutions A and B into separate cylinders. 7. Put some potassium ferricyanide into the flask, and place the funnel on the

flask. 8. Move the flask to a dark place. 9. Pour Solutions A and B into the flask at the same time, and watch what

happens Guide Questions:

1. How did you light up the solutions? What will mixing the solutions do? 2. What type of EM wave is produced? How is this EM wave produced? 3. Did the solution decrease its “glow” intensity as time passed by? Why? 4. What animals can you think of that use the mechanism similar to the solution

(emitting a similar type of EM wave)? Was it useful to that animal? Why? 5. If a specific organism can utilize an EM wave similar to the mixed solution, in

what ways can that organism use it? Cite an example. Part B: Chemiluminescence in a Stick Materials:

● glow stick (any color) ● timer

Procedure:

1. Light up the glow stick according to package instruction. 2. Observe how the light spread from one part to the rest of the stick. 3. Record the time it takes for the glow stick to lose its light. (You may opt to do

this in a dark room.) Guide Questions:

1. How did you light up the glow stick? What will bending the stick do to it? 2. What type of EM wave is produced? How is this EM wave produced? 3. Did the glow stick decrease its “glow” intensity as time passed by? Why? 4. What animals can you think of that use the mechanism similar to glow sticks

(emitting a similar type of EM wave)? Was it useful to that animal? Why? 5. If a specific organism can utilize an EM wave similar to glow sticks, in what

ways can that organism use it? Cite an example.


Learn about It

The branch of science studying the interaction between organisms and electromagnetic fields is known as bioelectromagnetics. In nature, various electromagnetic waves are used by organisms may it be for food production, attracting prey or as defense mechanisms. Photosynthesis One of the most popular use of electromagnetic waves is in photosynthesis. In this process, plants and other organisms, such as algae, use electromagnetic waves in the form of light as a source of energy to drive the reaction for food production. Steps in photosynthesis that require sunlight are known as light-dependent reactions, and in plants, they occur in the thylakoid membrane of chloroplasts—a vital organelle in plant cells. This energy absorption process uses chlorophyll and other pigments to take in sunlight.

Fig. 1. Plants use sunlight as a source of energy for photosynthesis.

In the light-dependent reactions of photosynthesis, the first step is to break water bonds into oxygen molecules and hydrogen atoms by using light energy from the sun or from a light source. This step takes place in the photosystem II. Electrons will be released from the splitting reaction. The electrons will move to the photosystem I, in which they will be energized again to be used by NADP+ to form NADPH, a component used to make sugar in the Calvin cycle. Due to the movement of free electrons, there will be a charge imbalance in the inside and outside of the thylakoid membrane. The movement of hydrogen ions through ATP


synthase will produce energy to convert ADP to ATP. NADPH produced will be sent to the next cycle, which is the light-dependent reaction. Because of selective light absorption, an object reflects a set of electromagnetic waves with a particular wavelength. This wavelength corresponds to the color seen by the eyes and enables color distinction between objects.

Fig. 2. Leaves absorb all the frequencies of light except for green.

Aside from being capable of reflecting and receiving electromagnetic radiation, some biological systems are also capable of emitting electromagnetic waves. Energy absorbed from light can also be converted to heat. This heat, also known as thermal radiation, is basically the release of energy as electromagnetic waves in the infrared region of the electromagnetic spectrum.

Bioluminescence Electromagnetic emission in the form of light is also present. The emitted light is usually a product of a series of chemical reactions in a general process known as chemiluminescence. A more specific kind of chemiluminescence is bioluminescence which takes place inside living organisms. An example of this phenomenon is the production of light by fireflies and some marine organisms. Light produced from chemiluminescence can be yellow, green, orange or blue. Bioluminescence is used by organisms for different purposes, some of which are for camouflage, illumination, defense, luring, sexual attraction, etc.


Brittle stars, for example, can distract their predators by detaching a glowing arm. They make their escape in the dark as the predators follow the detached body part. They simply regenerate their arms after.

Fig. 3. A brittle star which has detachable arms useful for distracting predators.

Anglerfish, on the other hand, use bioluminescence to attract prey. It has a fleshy growth called filament atop its head. The ball at the tip of this filament can light up, which smaller fish, being curious of it, approach for a closer look.

Fig. 4. A black devil anglerfish uses its filament at the top of its head to attract prey.

Adult fireflies use their bioluminescence to attract mates. Both male and female fireflies are capable of lighting up but most flashing fireflies in North America are male. Their flash patterns inform the nearby females their species and interest in mating.


Fig. 5. Fireflies, also known as lightning bugs.

There are also studies claiming cells to be capable of communicating through electromagnetic signaling in the UV region. It was proposed that this electromagnetic cell-to-cell signaling is induced by cells in a mitotic state or a stressed condition.

Key Points

● Bioelectromagnetics is the branch of science that studies the interaction between organisms and electromagnetic field.

● Photosynthesis is the process that uses electromagnetic waves in the form of light as a source of energy to produce food in plants and photosynthetic organisms.

● EM emissions in the form of light is being utilized by living organisms for several survival purposes. This mechanism is called bioluminescence.


Web Links

For further information regarding uses of EM waves in nature, visit the following links below:

● Read this article to know more about the contribution of glowing coral proteins in medical research Roach, John. 2015. ‘Glowing Coral Proteins Aid Medical Research.’ https://news.nationalgeographic.com/news/2005/01/0112_050112_coralproteins.html

● Watch this video to see the weird and wonderful world of bioluminescence. Widder, Edith. 2011. ‘The weird, wonderful world of bioluminescence’. https://www.ted.com/talks/edith_widder_the_weird_and_wonderful_world_of_bioluminescence/up-next

Check Your Understanding

A. Read and analyze the following statements given. Identify whether the statement is true or false in each item. Write T if the statement is true and F if otherwise. 1. The branch of science studying the interaction between organisms and

electromagnetic fields is known as bioelectromagnetics. 2. Photosynthesis and bioluminescence both utilize visible light in nature. 3. All phases of photosynthesis use electromagnetic waves. 4. Light-dependent reactions in photosynthesis needs UV rays. 5. Only green plants need light to function. 6. Thermal radiation is the release of energy as electromagnetic waves in

the infrared region of the electromagnetic spectrum. 7. Chemiluminescence is a process in which light is emitted from a series of

chemical reaction. 8. Chemiluminescence takes place in various organisms in nature. 9. Sexual attraction in living organisms utilizes bioluminescence. 10.Phytoplanktons utilize bioluminescence.


https://news.nationalgeographic.com/news/2005/01/0112_050112_coralproteins.html

https://www.ted.com/talks/edith_widder_the_weird_and_wonderful_world_of_bioluminescence/up-next

B. Identify whether the following organisms utilize EM wave(s) or not. Write U if the organism or species uses EM wave(s), and N if not. 1. Anglerfish uses bioluminescence to attract prey. 2. Dogs use sound waves through their nose to detect movement. 3. Adult fireflies use bioluminescence to attract mates. 4. Green light was supplied to green plants. 5. Phytoplanktons, when agitated in saltwater, gives of lights.

Challenge Yourself

Answer the following questions accordingly. 1. How and why do phytoplanktons produce visible light? 2. How do red-colored plants photosynthesize? 3. What other organisms use EM waves to survive? 4. What are the other applications of EM waves in nature? 5. Do you agree that EM waves are important in nature? Why?


Lesson 6.2: Technological Applications of Electromagnetic Waves


● learn the different uses of certain parts of electromagnetic spectrum;

● differentiate long distance and short distance utilization of electromagnetic waves;

● discuss how laser is produced; and ● discuss some X-ray and UV ray techniques.

The electromagnetic spectrum is composed of various types of waves with different characteristics due to their differences in wavelength,frequency and amount of energy carried. It is impossible for the innovative field of science to not notice the promising qualities of EM waves. Several inventions are developed by scientists, engineers, and inventors through the use of EM waves. What are some uses of EM waves in technology?

Warm-Up

Off you go! Materials:

● television with remote control ● mirror ● sheet of paper ● thick textbook ● meter stick

Procedure:

1. Test the responsiveness of the remote control to turn off the TV. 2. Try to turn off the TV using the following different procedures:


a. Position the mirror between you and the TV. Make sure to form a 90 degrees angle in the formation. Try to turn off the TV by pointing the remote control at the mirror instead of directly through the TV sensor.

b. Place a sheet of paper in front of the TV sensor. Try to turn off the TV. Do the same procedure using a thick textbook.

c. Try to turn off the TV at a distance of 1 meter. Try again for increments of 1 meter (2 m, 3 m, 4 m, …) until you can not turn the TV off.

Guide Questions:

1. What behavior of EM wave is exhibited in procedure 2.a.? Explain. 2. What behavior of EM wave is exhibited in procedure 2.b.? Explain. 3. Exhibiting these behaviors, can you confirm that an EM wave is being utilized

in TV-remote control sensors? 4. What is the maximum distance at which you can turn off the TV? Using this

“effectivity” distance, what could be the EM wave used in the sensors? Why?

Learn about It

Long Distance Communication Long distance communications, such as those using radios, televisions, tracking devices, satellites, and space probes, rely on transmission and reception of electromagnetic waves such as radio waves and microwaves.

Fig. 6. The Mobile User Objective System (MUOS) ground station at Naval Computer

and Telecommunications Area Master Station Pacific, Wahiawa, Hawaii.


An antenna converts electrical signals into radio signals and vice versa, but in practice, different antenna systems were designed for transmission and reception. For example, television and radio stations have very large antennae that transmit radio waves over a large area. These waves are picked up by antennae of television and radio units at homes and offices. Transmission is the process in which an antenna converts electric current to radio waves. Reception is the process in which an antenna converts received radio wave signals to electric current. Radio communications work by systematically adjusting some known property of electromagnetic waves such as amplitude or frequency. In amplitude modulation (AM), the difference in the amplitudes (i.e. signal strength) of the waves of this signal and carrier is modulated, that is, varied corresponding to the sound being transmitted. In frequency modulation (FM), the difference in frequency (and consequently wavelength) is varied instead of the amplitude. AM radio signals typically have a bigger reach compared to FM radio signals. A disadvantage of AM is the fact that it is harder to eliminate interference on the signal. Due to this, AM transmission is usually not used for transmission of music. Instead, it is typically used for voice communications and broadcasts, whereas FM is preferred for transmission of musical content. Microwaves are also used in long distance communication for systems such as the Global Positioning System (GPS) for navigation and mapping.

Short Distance Communication Wireless communications over short distances also require the use of electromagnetic waves. However, most of these applications require higher-energy electromagnetic waves such as microwave and infrared rays. Wireless Local Area Network (WLAN) uses microwaves to enable communications between the Wireless Access Point or WAP (the device that serves as hub or center of LAN), and the terminals (computers, laptops, mobile devices connected to LAN). Remote controls, such as those used in operating televisions, air conditioners, and other appliances, use infrared signals to operate.


Visible Light and Night Vision Among the electromagnetic waves, humans can only see visible light. However, upon using certain techniques or tools, those that are usually not visible with the naked eye can be seen. Night vision systems work by using infrared radiation as an additional input to visible light in producing images. Infrared emissions are associated with warm surface, or those with a higher relative temperature compared with the environment. CCTV cameras can be equipped with a night vision apparatus. Burglars can be confident entering a dark area thinking no one can see them, but an installed camera can “see ”and record them clearly using night vision. Some night vision systems also include an infrared source that acts as a “flashlight.” To the human observer, the surface appears dark because infrared is invisible to the naked eye. However, to the system, the area appears illuminated.

Fig. 7. A tactical air controller in night vision on a simulated target using lasers.

X-ray Techniques A material is said to be transparent to an electromagnetic wave when the radiation can pass through the material. Opaque materials are those that absorb (or reflect) electromagnetic waves. Paints contain traces of metals that are opaque to X-rays. Thus, X-ray techniques are also used to determine the authenticity of an artwork. It can provide a clue if a painting had been painted over. In ports, airports, and other establishments that require high security, X-ray scanners are used to detect what is inside luggage and boxes that enter these establishments.


Fig. 8. A baggage screening X-ray display.

Laser A laser device is made of a tube with mirrors on both ends and a material that can be stimulated to produce light. The gain medium can be stimulated using either light or electricity, which puts the atoms in high energy or excited state that will release energy by emitting coherent light. The material is stimulated until enough light is produced. One of the mirrors is slightly transparent, allowing coherent light to escape when it reaches a certain energy threshold. Lasers are used in a variety of cutting purposes. Laser cutting technology is used to cut metals and woods. It works by heating a thin region across a material allowing it to either burn or melt. The edge formed by the cut has a high-quality surface finish as compared to the output of mechanical cutting tools like the saw. Patterns can also be made from the holes or parts removed by the cut.

Fig. 9. A laser cutting machine which forms and cuts metals.


Laser is also commonly used in reading contents of an optical disk. The surface of this disk actually contains “pits” or microscopic regions that are sunk deeper than the surrounding materials. As the optical disk drive reads the surface of the optical disk, it sends the laser to its surface, which reflects it back to a detector. The pits cause the laser to reflect differently, representing data.

UV Radiation Since ultraviolet (UV) rays contain more energy than several other forms of electromagnetic waves, UV rays can be readily converted to heat or trigger chemical reactions when interacting with matter. Ultraviolet waves contribute to the production of free radicals that can also damage DNA. Thus, UV radiation is used to purify the air by destroying the DNA of airborne microorganisms. A reaction with an inert catalyst can also make UV radiation useful in dealing with pollutants, as most pollutants are carbon-based products that break down when exposed to ultraviolet radiation and inert catalysts. UV radiation can make some difficult-to-see substances more visible through fluorescence. Fluorescence is a phenomenon where substances absorb UV radiation and emit visible light. Chemicals that are capable of fluorescence are added to paper money, usually as ink with a certain pattern. This is why UV radiation can be used to detect counterfeit money. When an ultraviolet lamp shines on paper money, certain words and/or symbols appear indicating that the money is genuine.


Key Points

● EM waves have several applications in technology which includes the following:

○ Radio waves and microwaves are used in long distance communications such as that in AM and FM radio communications.

○ Microwaves are used in short distance such as in WLAN and those in remote controls of appliances.

○ Infrared are used in night vision systems of CCTV cameras. ○ Lasers used amplified light waves for detecting barcodes in groceries

and reading disk drives. ○ UV rays make some difficult-to-see substances more visible through

fluorescence. These waves are also used in detecting counterfeit money and air purification.

○ X-rays are utilized in scanners of airports and establishments.

Web Links

For further information regarding technological applications of EM waves visit the following links below:

● Read this article to understand more about lasers and the process of how it works. National Aeronautics and Space Administration, Space Place. 2017. ‘What is a laser?.’ https://spaceplace.nasa.gov/laser/sp/

● Watch this video to know how to spot a fake polymer bank note using a handheld UV fake money detector. Shopstuffltd. 2016. ‘Handheld UV Fake Money Detector / How To Spot A Fake Polymer Bank Note.’ https://www.youtube.com/watch?v=V74bHxImQ5A

● Watch this video to understand how X-rays see through your skin. Ted - Ed. 2015. ‘How X-rays see through your skin - Ge Wang.’ https://www.youtube.com/watch?v=gsV7SJDDCY4


https://spaceplace.nasa.gov/laser/sp/

https://www.youtube.com/watch?v=V74bHxImQ5A

https://www.youtube.com/watch?v=gsV7SJDDCY4


A. Given the following set of EM waves (radio waves, microwaves, infrared, visible light, UV ray, X-ray, gamma ray), write the wave that was correctly utilized in each situation or technology. 1. telephones 2. radio 3. Global Positioning Systems (GPS) 4. radar 5. wireless fidelity (Wi-fi) 6. night vision systems in CCTVs 7. security scanners in airports 8. laser 9. paper money scanners

10. camera phones

B. Enumerate other use or application for the following EM wave type specified. You may cite certain (electronic) devices which utilizes the EM wave. 1. visible light 2. infrared 3. microwave 4. UV ray 5. X-ray

Challenge Yourself

Answer the following questions. 1. What is the difference between long and short distance use of EM waves? 2. How are lasers produced? 3. In a house with Wi-Fi connectivity, why are some parts of the house unable to

receive or have poor Wifi signal? 4. Why do mountains and other high elevated places have poor

telecommunication signals? 5. Why are gamma rays not used in telecommunications?


Lesson 6.3: Applications of Electromagnetic Waves in Sanitation and Health


● know the practical applications of electromagnetic waves; and ● discuss the contributions of electromagnetic waves in the field of

medicine, sanitation and health.

The varying energy levels of electromagnetic waves interact differently with matter. Many of these interactions are capable of affecting living systems in such a way that they may be used for diagnosis, monitoring, and treatment of one’s health condition. Many regions of the electromagnetic spectrum are used in medicine. How are EM waves helpful in the field of medicine?

Warm-Up

Scanning X-rays Materials:

● computer or any electronic gadgets with internet connection Procedure:

1. Download the following photos and examine each.

● Examine the X-ray scan of a patella fracture on left knee. Moskito, Carlo Joseph. 2017. Patella fracture on the left knee.jpeg. Image. https://commons.wikimedia.org/wiki/File:Patella_fracture_on_the_left_knee.jpeg

● Examine the X-ray scan of bladder stones, urinary catheter and scoliosis Dilmen, Nevit. 2011. Medical XRay imaging AYB02 nevit.jpg. Image. https://commons.wikimedia.org/wiki/File:Medical_XRay_imaging_AYB02_nevit.jpg


● Examine the Cephalometric radiograph. ANUG. 2014. Cephalometric radiograph.JPG. Image. https://commons.wikimedia.org/wiki/File:Cephalometric_radiograph.JPG

Guide Questions:

1. What body system is being scanned by this machine? Can this machine scan other body systems? Why or why not?

2. What machine is used to produce X-ray scan results? What type of EM wave is used to produce these scans? How can you say so?

3. Why is X-ray the most applicable EM wave for the job of scanning bones? 4. Is X-ray also used in CT scans and ultrasounds? Why? 5. How does X-ray contribute to the improvement of treating ailments and

other operations in the medicine field?

Learn about It

Thermogram Infrared radiation can be used in medicine because of its interaction with cells and tissues. It is known to be useful for the treatment of strained muscles and tissues. It is also useful for the diagnosis of tumors since the higher cellular activity in tumors cause them to emit more infrared radiation than healthy tissues. This radiation emission can be seen with a thermogram. This equipment is known to simply monitor the heat and blood flow patterns on or near the surface of the body.

Fig. 11. A thermogram showing the heat and blood flow patterns on or near the

surface of the body.


Laser Surgery Lasers have a number of medical applications as well. A carbon dioxide (CO2) laser can be used for the treatment of tumors. An argon laser can be used for the repair of peripheral nerves. In cosmetic surgeries, argon lasers can be used for the removal of birthmarks. Bloodless surgeries also use laser cutting to cauterize (controlled burning) the tissues along the cut, and thus, immediately sealing the blood vessels, preventing too much blood loss. In LASIK or Laser-Assisted In Situ Keratomileusis surgery, a special laser is used to reshape the eye’s cornea for correcting the primary types of eye refractive error, such as myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. X-rays X-rays are commonly used for medical imaging. They can be used to take an image of the bones because the calcium in the bones tends to absorb X-rays while several other tissues, such as those of skin, muscles, and digestive tract are transparent to them. The “white” regions of an X-ray plate are actually the regions where the X-rays did not pass through. Most X-ray machines are not very useful in differentiating soft tissues because soft tissues are transparent to X-rays, but new models that are capable of surpassing this limitation are now available. To see the soft tissues using X-ray, doctors use contrast materials. Contrast materials are opaque to X-rays, allowing X-ray imaging of soft tissues to be visible. For example, swallowing barium sulfate coats the surface of the digestive tract, making it appear on X-ray plate and allowing its shape to be outlined.


UV Radiation Ultraviolet radiation, through fluorescence, is used to make hard-to-see materials, such as biological samples (blood, saliva, semen, etc.), glow especially in dark places. This is very useful in forensics, where remaining stains of bodily fluids that are otherwise invisible to the naked eye can be seen. Ultraviolet radiation can also be used for curing different skin conditions, such as acne. High energy electromagnetic radiations are also used in sterilization of food and equipment. Ultraviolet lamp is used in sterilizing work surfaces, such as those in laboratories and hospitals. It is also used as pasteurization agent to treat fruit juices and other food products.

Fig. 12. UV sterilization of pipettes and tips in a Biosafety Cabinet.

Gamma Ray Gamma rays are used in a new form of medical procedure called gamma-knife surgery; multiple beams of gamma rays are focused on a tumor to kill the cancerous cells. The beams are aimed at different angles to maximize the targeting of cancer cells while minimizing the damage to healthy tissues. Gamma ray is often used in the same manner to sterilize medical equipment. Food can also be treated using gamma rays to maintain freshness and flavor by killing microorganisms.


Key Points

● EM Waves, especially those with higher frequency, are used in sanitation and medical purposes. The following are some uses of these waves:

○ Infrared are used in thermogram for monitoring heat and blood flow in the human body.

○ Lasers are used in tumor removal, bloodless surgeries, and LASIK surgery.

○ UV rays are used in treatment of skin conditions, and sanitation of equipments.

○ X-rays are commonly used in medical imaging particularly in taking images of bones in the human body.

○ Gamma rays are used in killing cancer cells through targeting tumors and also used in sterilizing medical equipments.

Web Links

For further information regarding uses of EM waves in sanitation and health, visit the following links below:

● Watch this video to understand more about the use of gamma knife is used in a brain surgery. Dailymotion. 2008. ‘Gamma Knife: Brain Surgery without a Knife.’’ https://www.dailymotion.com/video/x7fsk4

● Watch this another video to know more about LASIK Surgery. Klinika Svjetlost. 2015. ‘How LASIK Surgery is Done HD Animation.’ https://www.youtube.com/watch?v=Xsg07RqvGFE

● Read this article to understand more about the different uses of electromagnetic waves found in nature. Just Science. 2018. ‘Applications of Electromagnetic Waves.’ http://www.justscience.in/articles/applications-of-electromagnetic-waves/2017/05/25


https://www.dailymotion.com/video/x7fsk4

https://www.youtube.com/watch?v=Xsg07RqvGFE

http://www.justscience.in/articles/applications-of-electromagnetic-waves/2017/05/25


A. Modify the underlined term in each item to make the statement true. If there is no need for replacement of the underlined term, write C. 1. X-rays are commonly used for medical imaging. 2. Bloodless surgery uses laser cutting to cauterize the tissues along the cut. 3. The white regions of an X-ray plate are actually the regions where the

X-rays passed through. 4. Ultraviolet radiation can also be used for curing acne. 5. Gamma ray is often used to sterilize medical equipment.

B. Match column A with the medical procedure to be done on each situation on

column B then match column B with the EM wave utilized in the procedure.

Column A Column B Column C

1-2. Ben consulted an ophthalmologist to make his eye have a perfect 20/20 vision.

3-4. A patient was

diagnosed with brain tumor.

5-6. A dermatologist

conducts removal of skin warts and birthmarks.

7-8. A confined patient’s

body heat flow is being monitored.

9-10. Sarah had a sprain

accident while playing basketball. Her parents insists on knowing if she has a bone fracture.

a. thermogram b. laser operation

c. LASIK

d. X-ray scan

e. sterilization

f. gamma-knife

surgery

i. radiowave

ii. microwave

iii. infrared

iv. visible light

v. UV ray

vi. X-ray

vii. gamma ray


Challenge Yourself

Answer the following questions. 1. Which practical application of electromagnetic waves is the most important

for you? Why? 2. How did EM wave contribute to the innovations in the field of medicine? 3. What are the consequences of using or undergoing operations which utilizes

EM waves? 4. Do the benefits of using EM waves in the medicine field out-weighted the

consequences? Why? 5. Which is more convenient to use in sterilization: gamma ray or UV ray? Why?


Lesson 6.4: Hazards of Electromagnetic Waves


● cite hazards in using or being exposed to some EM waves; ● differentiate ionizing and non-ionizing radiation; and ● discuss the effects of UV radiation in living things and

environment.

Despite the numerous uses and benefits of electromagnetic waves, certain forms of radiation still pose a great threat on the health of different organisms, especially humans. What are these hazards imposed when exposed to certain EM waves?

Warm-Up Sunbathing Newspaper

Materials: ● 3 pieces 2 square inches newspaper cut-out (text part of newspaper) ● 3 pieces 2.5 square inches transparent plastic cover ● 1 piece 2 square inches black paper ● sunblock lotion ● transparent adhesive tape

Procedure:

1. For set-up 1, place the plastic cover on top of a piece of newspaper cut-out. Secure using adhesives.

2. For set-up 2, place the plastic cover on top of a piece of black paper which is layered above the newspaper cut-out. Secure using adhesives.

3. For set-up 3, place the plastic cover on top of a piece of newspaper cut-out. Secure using adhesives. Apply sunblock lotion on the plastic cover.

4. Expose the three set-up under the direct sun for 3 hours. 5. Remove the plastic covers and compare the newspaper cut-out.


Guide Questions: 1. What happened to the newspaper cut-out in each set-up? Describe each. 2. Which newspaper cut-out has the most faded print? Why did this happen? 3. Which newspaper cut-out has the least faded print? 4. Which “cover” protected the print the most? Why? 5. What EM wave from the sun caused the print to fade? Is this wave harmful to

humans? Give an example.

Learn about It

Ionizing and Non-ionizing Radiation There are two broad types of electromagnetic radiation: ionizing radiation and non-ionizing radiation. Ionizing radiation comes from electromagnetic waves with sufficiently high energy that can possibly cause cellular and DNA damage. Examples of ionizing radiation include UV radiation, X-rays and gamma rays. Non-ionizing radiation are from electromagnetic waves with relatively low radiation levels believed to be harmless to humans. Some non-ionizing radiation include extremely low frequency radio (ELF) waves, radio (RF) waves, microwaves and visual light. The major effect of non-ionizing radiation is an increase in the system’s temperature. Ionizing radiation, on the other hand, poses a greater threat. For a 70 kg human, 1.5 million joules of non-ionizing radiation is required to cause death. Same effect will be observed on 300 joules of X-ray, an ionizing radiation. Ultraviolet Radiation Ultraviolet radiation has three sub classifications namely: UV A, UV B and UV C. UV A has the lowest frequency among the three. UV B has a slightly lower frequency than UV C but is already capable of causing severe sunburn and cellular damage. Overexposure of plants to UV B impairs photosynthesis and could result in reduced size, productivity and quality of crops. Phytoplankton’s exposure to UV B reduces their capability to carry out photosynthesis. UV C, having the highest frequency causes severe cell damage. Overexposure to UV radiation also affects the flowering times of some plants, and in consequence could affect the animals that depend on them.


Fig. 13. UV exposure affects flowering times of plants.

Ultraviolet radiation can also reconfigure oxygen into ozone. Ozone is a very reactive variant of oxygen that is harmful in large amounts. UV radiation has the ability to permanently reconfigure compounds with double bonds, including several biological molecules such as the DNA. Thus, ultraviolet is capable of damaging the DNA of different organisms, including humans. X-rays and gamma rays are also capable of causing cell damage, which can result in mutations that may potentially lead to cancer and death.

Fig. 14. Effect of using sunscreen as protection to UV rays.


Key Points

● Ionizing radiation comes from electromagnetic waves with sufficiently high

energy that can possibly cause cellular and DNA damage. ● Examples of ionizing radiation are UV radiation, X-rays, and gamma rays. ● Non-ionizing radiation comes from electromagnetic waves with relatively

low radiation levels believed to be harmless to humans. ● Examples of non-ionizing radiation are radio waves, microwaves and visible

light. ● Ultraviolet radiation has classifications namely: UV A, UV B and UV, in

increasing frequency. UV C poses the greatest danger among the three.

Web Links

For further information regarding hazards of EM waves, visit the following links below:

● Read this article to know more about the SPF sunscreens which is used as a protection against harmful UV rays. Fung, Brian. 2012. ‘What SPF Does And Doesn't Tell You About Your Sunscreen.’ https://www.theatlantic.com/health/archive/2012/08/what-spf-does-and-doesnt-tell-you-about-your-sunscreen/261180/

● Watch this video to understand more the effects of EM radiation on health and some tips to prevent health problems with regards to this kind of radiation. Enviro Chip. 2014. ‘Effects of Electromagnetic Radiation on Health and Tips to Prevent Health Problems.’ https://www.youtube.com/watch?v=APJw7fpeuFQ

● Watch this another video to know how dangerous X-rays are to human beings. Seeker. 2015. ‘How Dangerous Are X-rays?’ https://www.youtube.com/watch?v=vmdemMnkSKo


https://www.theatlantic.com/health/archive/2012/08/what-spf-does-and-doesnt-tell-you-about-your-sunscreen/261180/

https://www.youtube.com/watch?v=APJw7fpeuFQ

https://www.youtube.com/watch?v=vmdemMnkSKo


A. Determine if the following use of EM waves outweighs the benefits than the hazards. Put an “X” mark to the box that corresponds to the item/scenario in which the hazard outweighs the benefit of utilizing EM waves.

⬜ 1. sunbathing for 3 hours under direct sunlight

⬜ 2. living near nuclear power plants

⬜ 3. undergoing X-ray scan thrice a month

⬜ 4. microwaving food

⬜ 5. exposing plants to UV B

⬜ 6. exposing flowering plants to UV A

⬜ 7. cell mutation

⬜ 8. prolonged use of AM radio

⬜ 9. calling through cellular phones

⬜ 10. using infrared thermometer for monitoring body temperature

B. Read and analyze the following statements given. Identify the term being

described in each item. 1. It comes from electromagnetic waves with sufficiently high energy that

can possibly cause cellular and DNA damage. 2. It comes from electromagnetic waves with relatively low radiation levels

believed to be harmless to humans. 3. It has the lowest frequency among the three subtypes of UV rays. 4. It is the UV ray subtype used in sanitation and sterilization. 5. It is the UV ray subtype present in sunlight.


Challenge Yourself

Answer the following questions.

1. What are the hazards in using or being exposed to UV rays? 2. What is the difference between ionizing and non-ionizing radiation? 3. Is “radiation” a bad effect of using EM waves? Why? 4. What could be an advantage of ionizing radiation from non-ionizing

radiation? 5. Prolonged usage of call features in cellular mobile phones is found to be

dangerous for the brain. What advice can you give to cell phone users?


Laboratory Activity

Activity 6.1 Comparison of Sunblock Lotions with Different SPFs

Objectives At the end of this laboratory activity, the students should be able to:

● cite hazards in using or being exposed to UV rays; ● determine which SPF is effective in protecting the newspaper from fading

against UV rays; and ● determine which sunblock lotion is the most cost-efficient.

Materials and Equipment

● sunblock lotions with SPF 15, 30, 50, 100, and 150 (10 g each) ● newspapers ● 5 pieces 2” by 2” newspaper cut-out ● transparent plastic cover ● transparent adhesive tape ● marker ● timer

Procedure

1. Cut five pieces of newspaper with a length and width of 2 inches each. 2. Assemble the news newspaper cut-outs side-by-side with a 1.5” space in

between. 3. Cover the newspaper cut-outs with plastic cover. 4. Secure the cover of the cut-outs with adhesives. 5. Apply sunblock lotion generously to the cover of the newspaper cut-out.

Make sure to label your set-up with the SPF of the lotion applied. 6. Leave the set-up under direct sunlight for 4 hours. 7. Observe what will happen to the newspaper cut-outs. Take note of your

observations. 8. You may use a similar table to table 1 for contrasting the outcome.


Data and Results Table 1. Newspaper cut-out protected by sunblock lotions with various SPF under exposures to direct sunlight for 4 hours.

Sunblock SPF Newspaper cut-out

15

30

50

100

150

Guide Questions

1. What happened to the newspaper cut-out after exposure under the direct sunlight? What causes this change?

2. What type of EM wave caused this change? What hazards can you think of in being exposed to this type of EM wave?


3. Which SPF among the sunblock lotions protected the newspaper from fading?

4. What relationship between the SPF and the fading of the newspaper text can you generalize for the span of 4 hours exposure under the sun?

5. Considering the cost and effectivity of the SPF sunblock lotion for 4 hours direct sunlight exposure, which SPF value is the most cost-efficient?

Performance Task

Bioluminescence tourism Goal

● Your group’s goal is to design a product or project to utilize bioluminescence from excessive phytoplankton population in a beach in Coron, Palawan.

Role

● Your group is a group of recreation designers who help the Department of Tourism in Palawan to promote tourism without compromising the environment.

Audience

● Your audience is the Department of Tourism product and project accreditation department.

Situation

● Your group helps the Department of Tourism in promoting tourism in the island of Palawan. In a certain beach in Coron, Palawan, the population of phytoplanktons (making the beach glow) is increasing rapidly, which will cause an imbalance in the beach’s ecosystem.

Product, Performance, and Purpose:

● Your group will design a product or project which utilizes the bioluminescence of the phytoplanktons, and will promote tourism in Coron at the same time. Your output and performance will be an oral presentation with supporting Powerpoint presentation for the proposed product design or project plan.


Standards and Criteria Your performance and output will be graded on the following criteria:

Criteria Below Expectations, 0% to 49%

Needs Improvement

50% to 74%

Successful Performance 75% to 99%

Exemplary Performance

100%

Content. Detailed facts are presented well. Content related to the task.

Details not presented. Content is not related to the task.

Details are presented but not organized. There are some content that are not related to task.

Details are presented in an organized manner.Content are related to the task.

Details are presented in an organized matter that can be easily understood. Content are related to the task. Additional supporting details are presented.

Communication Skills. Presentation was done in a clear and logical manner.

Presentation was not done.

Presentation was done but in a disorganized and illogical manner.

Presentation was done smoothly but the concepts are presented in such a way that should be rearranged for better understanding.

Presentation was done clearly. Concepts were presented in a logical manner and easily understandable by the audience.

Self Check

After studying this unit, can you now do the following?

Check I can…

enumerate uses and application of EM waves in nature, technology, sanitation and health

discuss the relevance of the uses and application of EM waves in nature, technology, sanitation and health

discuss the contribution of EM waves in the field of medicine

cite hazards in using or being exposed to some EM waves


Key Words

amplitude modulation (AM)

It is a type of modulation wherein the difference in the amplitudes (i.e. signal strength) of the waves of this signal and carrier is modulated, that is, varied corresponding to the sound being transmitted.

Bioelectromagnetics It is a branch of science which studies the interaction between organisms and electromagnetic fields.

Bioluminescence It is a more specific kind of chemiluminescence in which the chemical reaction takes place in a living organism.

Chemiluminescence It is a general process when light emitted is a product of a series of chemical reactions.

Fluorescence It is a phenomenon where substances absorb UV radiation and emit visible light.

frequency modulation (FM)

It is a type of modulation wherein the difference in frequency (and consequently wavelength) is varied instead of the amplitude.

Ionizing radiation It comes from electromagnetic waves with sufficiently high energy that can possibly cause cellular and DNA damage.

Laser Laser is an acronym coined from the process that allows the generation of coherent light; laser stands for Light Amplification by Stimulated Emission of Radiation.

Non-ionizing radiation It comes from electromagnetic waves with relatively low radiation levels believed to be harmless to humans.

Photosynthesis It is a process in which plants and other photosynthetic organisms use electromagnetic waves in the form of light as a source of energy.

Radar It is a tracking system that sends out radio waves and detects the waves that bounce back. It can determine the location and speed of the object being tracked, such as a passing airplane.


Wrap Up

Some Uses of Electromagnetic Waves

Photo Credits

Unit photo. AEHF 1 (https://commons.wikimedia.org/wiki/File:AEHF_1.jpg) by USAF (Los Angeles AFB) is marked as a public domain via Wikimedia Commons.

Figure 3. Brittle starfish in kona

(https://commons.wikimedia.org/wiki/File:Brittle_starfish_in_kona.jpg) by Brocken Inaglory is licensed under CC BY-SA 3.0 via WikimediaCommons.

Figure 4. Ha - Melanocetus johnsonii 2

(https://commons.wikimedia.org/wiki/File:Ha_-_Melanocetus_johnsonii_2.jpg) by Emőke Dénes is licensed under CC BY-SA 4.0 via Wikimedia Commons.

Figure 5. Lupines and Fireflies No. 4 (14505155544)

(https://commons.wikimedia.org/wiki/File:Lupines_and_Fireflies_No._4_(14505155544).jpg) by Mike Lewinski from Tres Piedras, NM, United States is licensed under CC BY 2.0 via Wikimedia Commons.


Figure 6. The Mobile User Objective System (https://commons.wikimedia.org/wiki/File:The_Mobile_User_Objective_System.jpg) by Mass Communication Specialist 2nd Class John W. Ciccarelli Jr. is marked as public domain via Wikimedia Commons

Figure 7. A tactical air controller aims a laser target designator on a simulated

target ( http://www.pacaf.af.mil/shared/media/photodb/photos/070712-F-2207D-111.jpg) by Senior Airman Steven R. Doty, USAF is marked as public domain via Wikimedia Commons

Figure 8. Xray-verkehrshaus

(https://commons.wikimedia.org/wiki/File:Xray-verkehrshaus.jpg) uploaded by IDuke at English Wikipedia is licensed under CC BY 2.5 via Wikimedia Commons.

Figure 10. US $20 under blacklight

(https://commons.wikimedia.org/wiki/File:US_$20_under_blacklight.jpg) by Scott Nazelrod is marked as public domain via Wikimedia Commons

Figure 11. Thermogram

(https://commons.wikimedia.org/wiki/File:Thermogram.jpg) by Alexmj is licensed under CC-BY-SA 3.0 via Wikimedia Commons.

Figure 12. UV Sterilisation

(https://commons.wikimedia.org/wiki/File:UV_Sterilisation.jpg) by Orla Keogh is licensed under CC BY 4.0 via Wikimedia Commons.

Figure 12. Flowers-Garden-Ireland-Plants

(https://commons.wikimedia.org/wiki/File:Flowers-Garden-Ireland-Plants.JPG) by Ciaran036 is licensed under CC0 1.0 via Wikimedia Commons.

Figure 13. UV and Vis Sunscreen

(https://commons.wikimedia.org/wiki/File:UV_and_Vis_Sunscreen.jpg) by Spigget is licensed under CC BY-SA 3.0 via Wikimedia Commons.


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unit 6 uses of electromagnetic waves

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