chapter 3 chapter 3: the electromagnetic spectrum section 2 section 2: waves of the electromagnetic...


Post on 20-Jan-2016




0 download

Embed Size (px)


PowerPoint Presentation

Chapter 3: The Electromagnetic SpectrumSection 2: Waves of the Electromagnetic Spectrum

I. What is the Electromagnetic Spectrum? A. All electromagnetic waves travel at the same speed in a vacuum, but they have different wavelengths and different frequencies.1. Visible light = radiation in the wavelengths you can see a. small portion of electromagnetic radiation is visible lightb. Rest is invisible 2. Different wavelengths for different types of waves.3. recall: speed = wavelength x frequency a. so, as the wavelength decreases, the frequency increases

a. Waves with the longest wavelengths have the lowest frequenciesb. amount of energy carried by and EMW increases with frequencyB. The electromagnetic spectrum- is the complete range of electromagnetic waves placed in order of increasing frequency.1. The electromagnetic spectrum is made up of radio waves, infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays.

II. Radio Waves A. Radio Waves- are the electromagnetic waves with the longest wavelengths and lowest frequencies. 1. Examplea. Broadcast waves: radio and televisionb. Microwaves2.Broadcast waves- these are radio waves with longer wavelengths.a. Radio or TV antenna picks up these waves at certain frequenciesb. Then converted to an electrical signal which isconverted to sound (radio) sound and picture (TV)

B. Microwaves radio waves with the shortest wavelengths and the highest frequencies 1. used in cooking, radar, and cellular phone communication a. Radar = radio detection and ranging b. Radar is a system that uses reflected radio waves to detect objects and measure their distance and speed.1. distance determined by how long it takes the reflected waves to return to the device2. Speed determined by the doppler effecta. Frequency of reflected waves off of car is different from the original waves b. Difference in frequency is the speed

III. Infrared Rays A. Infrared rays- are electromagnetic waves with wavelengths shorter than those of radio waves. 1. have more energy than radio waves bc they have a higher frequencyEx: the invisible heat (infrared radiation) you feel as burner warms up before you see the glow B. Heat lamps:1. bulbs give off infrared rays (often called heat rays) and very little visible light.

B. Infrared Cameras- 1. take pictures using infrared rays instead of lighta. Most objects give off some infrared rays.2. thermogram- an image that shows regions of different temperatures in different colors3. used to see objects in the dark4. firefighters use infrared cameras to locate fire victims inside a dark or smoky building.

Visible Light A. Visible light electromagnetic waves you can see 1. shorter wavelengths and higher frequencies than infrared rays a. Red light = longest wavelengths b. All other colors appear as the wavelengths decreasec. Violet light = shortest wavelengthd. White light = mixture of many colors2. use a prism to separate out white light from the suna. Waves bend as they enter a new mediumb. Therefore, the prism refracts different wavelengths by different amounts and separates them into different colors.1. red light waves refract the least2. violet light waves refract the most

V. Ultraviolet RaysA. Ultraviolet rays electromagnetic waves with wavelengths just shorter than those of visible light.1. have higher frequencies than visible light = more energy2. energy is great enough to damage or kill living cells.Ex: UV lamps used to kill bacteria on hospitals equipment 3. small doses of UV is beneficial to health: produces vitamin D (needed for teeth and bones)4. large doses is dangerous = burn skin, cause skin cancer, damage eyes

VI. X-Rays- A. X-Rays- are electromagnetic waves with wavelengths just shorter than those of ultraviolet rays. 1. have higher frequencies and carry more energy than UV rays2. can penetrate most mattera. Except bone or dense matter = absorbs the x-rays = does not pass through3. too much exposure to x-rays can cause cancer4. lead apron absorbs x-rays preventing them from reaching your body

VII. Gamma Rays A. Gamma rays- are the electromagnetic waves with the shortest wavelengths and highest frequencies1. most penetrating of all electromagnetic waves2. can be produced from some radioactive substances and nuclear reactions3. used in medicine: kill cancer cellsa. Patient injected with a fluid that emits gamma rays = forming an image inside the body4. Explosions of starts are thought to produce gamma rays in the space