1. Chapter 17 - Light An electromagnetic wave is composed of electric and magnetic fields that are vibrating perpendicular to each other. An electromagnetic wave is composed of electric and magnetic fields that are vibrating perpendicular to each other.

2. What is polarized light? What is polarized light? When light goes through a polarized filter only vibrations of one direction are allowed through. When light goes through a polarized filter only vibrations of one direction are allowed through. Polarized light – light that is vibrating only in one direction. Polarized light – light that is vibrating only in one direction.

3. Light acts like both a particle and a wave Light acts like both a particle and a wave Photoelectric effect – when light “particles” knock electrons off of a surface. Photoelectric effect – when light “particles” knock electrons off of a surface. Photon – a particle of light Photon – a particle of light

4. Radio waves – generated and absorbed by electrons pulsing back and forth along a wire (low energy wave) Radio waves – generated and absorbed by electrons pulsing back and forth along a wire (low energy wave) Long infrared waves – used in some communications (cell phones) Long infrared waves – used in some communications (cell phones) Short infrared (heat waves) – produced and absorbed by molecular vibrations, produced in microwave ovens. Short infrared (heat waves) – produced and absorbed by molecular vibrations, produced in microwave ovens.

5. Visible light – created and absorbed by electrons dropping down energy levels. The difference in energy of the energy levels corresponds to the wavelength of light emitted. Visible light – created and absorbed by electrons dropping down energy levels. The difference in energy of the energy levels corresponds to the wavelength of light emitted. Ultraviolet light – (beyond violet) (black light) cause sunburn and skin cancer, helps skin provide vitamin D Ultraviolet light – (beyond violet) (black light) cause sunburn and skin cancer, helps skin provide vitamin D

6. X-rays – penetrated the body, absorbed by dense tissue (bone). Will darken a photographic plate. X-rays – penetrated the body, absorbed by dense tissue (bone). Will darken a photographic plate. Gamma rays – comes from all regions of space, like tiny bullets passing through body. Used to help treat cancer. Gamma rays – comes from all regions of space, like tiny bullets passing through body. Used to help treat cancer.

7. All electromagnetic waves travel the same speed but they all have different frequency and wavelength. All electromagnetic waves travel the same speed but they all have different frequency and wavelength. What is the relationship between wavelength and frequency? What is the relationship between wavelength and frequency? The higher the frequency, the shorter the wavelength The higher the frequency, the shorter the wavelength The lower the frequency, the longer the wavelength. The lower the frequency, the longer the wavelength. The longer the wavelength the lower the energy The longer the wavelength the lower the energy

8. What is radar? How does radar work? What is radar? How does radar work? Radio detection and ranging is done by sending a pulse of radio waves. The time it takes for them to return gives the distance to the object. Radio detection and ranging is done by sending a pulse of radio waves. The time it takes for them to return gives the distance to the object. The change in frequency as the waves bounce off the object can be used to determine how fast the object is going. The change in frequency as the waves bounce off the object can be used to determine how fast the object is going. The police radar gun uses the Doppler effect to determine your speed. The police radar gun uses the Doppler effect to determine your speed.

9. What is Magnetic Resonance Imaging (MRI)? What is Magnetic Resonance Imaging (MRI)? A short burst of radio waves, along with a strong magnetic field cause a person’s atoms to line up with the magnetic field. A short burst of radio waves, along with a strong magnetic field cause a person’s atoms to line up with the magnetic field. The atoms return to a random arrangement at different rates and this is used to give an image of soft tissues such as the brain. The atoms return to a random arrangement at different rates and this is used to give an image of soft tissues such as the brain.

10. Infrared rays and thermograms Infrared rays and thermograms Infrared cameras and thermograms allow us to see heat radiation. One application is determining areas of greatest heat loss in homes. Infrared cameras and thermograms allow us to see heat radiation. One application is determining areas of greatest heat loss in homes.

11. Incandescent light Incandescent light Incandescent lights have a tungsten filament that gets “white hot” Incandescent lights have a tungsten filament that gets “white hot” Most of the energy given off is heat radiation (less than 10% efficient) Most of the energy given off is heat radiation (less than 10% efficient)

12. How do fluorescent lights work? How do fluorescent lights work? Ultraviolet light is created as an electric current passes through a vapor Ultraviolet light is created as an electric current passes through a vapor The inside of the light is coated with a phosphor which glows when hit with U.V. light The inside of the light is coated with a phosphor which glows when hit with U.V. light They are more efficient than incandescent lights. They are more efficient than incandescent lights. Sea shells under black fluorescent light

13. Bioluminescence – what is it? Bioluminescence – what is it? A chemical reaction within an organism produces light (firefly). A chemical reaction within an organism produces light (firefly). Artificial bioluminescence created by genetic engineering in a tobacco plant

14. AM and FM waves, what are they? How are they different? AM and FM waves, what are they? How are they different? A.M. : Amplitude modulation – the amplitude of a wave is changed to carry information. A.M. : Amplitude modulation – the amplitude of a wave is changed to carry information. F.M. : Frequency modulation – the frequency is modulated to carry information. F.M. : Frequency modulation – the frequency is modulated to carry information.