light and electromagnetic waves & the electromagnetic spectrum

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  • Light and Electromagnetic Waves &the Electromagnetic Spectrum

  • Light and the Eye

  • NATURE OF WAVESWaves (Def.) A wave is a disturbance that transfers energy through vibrations.

    Medium/Matter Substance or region through which a wave is transmitted.

    Speed of Waves Depends on the properties of the medium.

    2000 Microsoft Clip Gallery

  • Part 1 Properties of LightLight travels in straight lines:

  • Light travels VERY FAST around 300,000 kilometres per second.

    At this speed it can go around the world 8 times in one second.

  • Light travels much faster than sound. For example:

    Thunder and lightning start at the same time, but we will see the lightning first.

    2) When a starting pistol is fired we see the smoke first and then hear the bang.


  • Properties of LightWhen light strikes an object it is:ReflectedTransmitted Absorbed

  • Properties of LightColor of objects is the color it reflectsEx- an orange is orange because it absorbs every color BUT orange, instead it reflects orange If you do not shine orange light on it, it will appear blackBlack is the absence of color, white is the blending of all colors

  • Properties of LightReflection- when an object or wave bounces back off a surface

  • Properties of LightReflection- when an object or wave bounces back off a surface Law of reflection- angle made from incoming wave = the angle made from reflected wave

  • Properties of LightRefraction- bending of light waves due to a change in speed

  • LIGHT: Refraction of LightRefraction Bending of light due to a change in speed. Index of Refraction Amount by which a material refracts light.Prisms Glass that bends light. Different frequencies are bent different amounts & light is broken out into different colors.

  • Properties of LightRefraction- bending of light waves due to a change in speedLens- curved glass or transparent material that refracts lightConvex lens- thicker in the center than the edges (bends light in)


  • PowerPoint created by Mrs. B-D 2007Light, Lens, Action!From the moment you wake up in the morning to the time you go to sleep at night, your eyes are acting like a video camera. Everything you look at is then sent to your brain for processing and storage much like a video. This is a very simplified explanation, but as you read on, you will discover why the sense of sight is actually considered the most complex of the five senses.

  • PowerPoint created by Mrs. B-D 2007How the Eye WorksTake a moment to locate an object around you. Do you know how you are able to see it? Would you believe that what you are actually seeing are beams of light bouncing off of the object and into your eyes? It is hard to believe, but it is true.

    The light rays enter the eye through the cornea, which is a thick, transparent protective layer on the surface of your eye. Then the light rays pass through the pupil (the dark circle in the center of your eye) and into the lens.

    PowerPoint created by Mrs. B-D 2007

  • PowerPoint created by Mrs. B-D 2007How the Eye Works continuedYour lens in your eyes change size all the time. When you look at objects real close up, the lens gets thicker. If you look at objects far away, it gets thinner. It does this to help you focus the correct image on the retina.

    After light passes through the lens it shines through the back of the eye where it hits the retina. The retina takes the light and changes it into nerve impulse so the brain can understand what the eye sees. It sends the message to the brain by way of the optic nerve.

    PowerPoint created by Mrs. B-D 2007

  • PowerPoint created by Mrs. B-D 2007Parts of the Eye

    PowerPoint created by Mrs. B-D 2007

  • PowerPoint created by Mrs. B-D 2007Cornea: The cornea is a clear white covering over the outside of the eye. It helps the eye focus like a lens on a camera.Iris: The iris is the part of your eye that has color. It gets bigger and smaller to let in different amounts of light.Pupil: Black opening in the middle of the eye. Light comes through this opening.

    PowerPoint created by Mrs. B-D 2007

  • PowerPoint created by Mrs. B-D 2007Lens: The lens bends light. This helps the eye see close up and far away things.Retina: The retina has nerve cells called rods and cones that detect light. It is in the back of your eye.Optic Nerve: The optic nerve carries electrical signals from your retina to your brain so you can see.

    PowerPoint created by Mrs. B-D 2007

  • PowerPoint created by Mrs. B-D 2007Rods and Cones Rods and cones are special cells that process light. Rods and cones are extremely small. In fact, there are about 120 million rods and 7 million cones in each eye! Rods help us see black and white and shades of grey. Cones help us see color. You have three kinds of cones are - red, green, and blue. These cones work together to help us see millions of colors.

  • PowerPoint created by Mrs. B-D 2007Flipped Image When you see images, they turn upside down when they hit the retina. So your brain sees everything in the world upside down. Your brain basically flips everything around so it is right side up again.

  • Electromagnetic Spectrum

  • Electromagnetic WavesTransverse waves without a medium! (They can travel through empty space)

  • They travel as vibrations in electrical and magnetic fields.Have some magnetic and some electrical properties to them.

  • When an electric field changes, so does the magnetic field. The changing magnetic field causes the electric field to change. When one field vibratesso does the other.

    RESULT-An electromagnetic wave.

  • Waves or Particles?Electromagnetic radiation has properties of waves but also can be thought of as a stream of particles.Example: LightLight as a wave: Light behaves as a transverse wave which we can filter using polarized lenses.Light as particles (photons): When directed at a substance light can knock electrons off of a substance (Photoelectric effect)

  • Electromagnetic Spectrumname for the range of electromagnetic waves when placed in order of increasing frequencyRADIO WAVESMICROWAVESINFRARED RAYSVISIBLE LIGHTULTRAVIOLET RAYSX-RAYSGAMMA RAYS

  • Notice the wavelength is long (Radio waves) and gets shorter (Gamma Rays)

  • RADIO WAVESHave the longest wavelengths and lowest frequencies of all the electromagnetic waves.

  • Global Positioning Systems (GPS) measure the time it takes a radio wave to travel from several satellites to the receiver, determining the distance to each satellite.

  • A radio picks up radio waves through an antenna and converts it to sound waves.Each radio station in an area broadcasts at a different frequency. # on radio dial tells frequency.

  • MRI (MAGNETIC RESONACE IMAGING) Uses Short wave radio waves with a magnet to create an image.

  • MICROWAVESHave the shortest wavelengths and the highest frequency of the radio waves.

  • Used in microwave ovens.Waves transfer energy to the water in the food causing them to vibrate which in turn transfers energy in the form of heat to the food.

  • RADAR (Radio Detection and Ranging)Used to find the speed of an object by sending out radio waves and measuring the time it takes them to return.

  • INFRARED RAYSInfrared= below redShorter wavelength and higher frequency than microwaves.

  • You can feel the longest ones as warmth on your skin Warm objects give off more heat energy than cool objects.

  • Thermograma picture that shows regions of different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off. Therefore people give off infrared rays.

    Heat lamps give off infrared waves.

  • VISIBLE LIGHTShorter wavelength and higher frequency than infrared rays.Electromagnetic waves we can see.Longest wavelength= red lightShortest wavelength= violet (purple) light

  • When light enters a new medium it bends (refracts). Each wavelength bends a different amount allowing white light to separate into its various colors ROYGBIV.

  • ULTRAVIOLET RAYSShorter wavelength and higher frequency than visible lightCarry more energy than visible light

  • Used to kill bacteria. (Sterilization of equipment)

  • Too much can cause skin cancer.Use sun block to protect against (UV rays)

  • Causes your skin to produce vitamin D (good for teeth and bones)

  • X- RAYSShorter wavelength and higher frequency than UV-raysCarry a great amount of energyCan penetrate most matter.

  • Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed)

  • Too much exposure can cause cancer (lead vest at dentist protects organs from unnecessary exposure)

  • Used by engineers to check for tiny cracks in structures.The rays pass through the cracks and the cracks appear dark on film.

  • GAMMA RAYSShorter wavelength and higher frequency than X-raysCarry the greatest amount of energy and penetrate the most.

  • Used in radiation treatment to kill cancer cells.Can be very harmful if not used correctly.

  • The Incredible Hulk was the victim of gamma radiation.

  • Exploding nuclear weapons emit gamma rays.

  • Brief SUMMARYA. All electromagnetic waves travel at th


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