Section 2 review
When white light passes through a glass prism, blue light is refracted more strongly than red light, resulting in dispersion; glass has a higher index of refraction for blue light than for red light. While all colors of light travel at the same speed in a vacuum, light of different colors travels at different speeds through a medium such as glass. The refractive index of a material represents the ratio of the speed of light in a vacuum to the speed of light in the material. Electromagnetic waves or light do not only come in the visible colors that you can see in a rainbow or in light dispersed by a prism. Electromagnetic radiation encompass a broad spectrum of waves, from low-frequency radio waves and microwaves to high-frequency x-rays and gamma rays. The electromagnetic spectrum is used in many different modern technologies. Read the text aloud
dispersion, index of refraction, electromagnetic spectrum, radiation, spectrum, gamma rays, x-rays, ultraviolet light, infrared radiation, microwaves, radio waves

n= c v

Review problems and questions

  1. Describe one piece of technology that is based on each of the following wavelength regimes of the electromagnetic spectrum: x-ray, visible, infrared, microwave, and radio. Read the text aloud Show
  1. Compare photons detected by a CCD digital camera and a thermal imaging camera. Which photons have a longer wavelength? Which have a higher frequency? Read the text aloud Show
  1. Astronomical observations at 1 THz can only be made at high elevations where there is little water vapor. What wavelength is this light? In what part of the electromagnetic spectrum does it fall? Read the text aloud Show
  1. How might a doctor use visible radiation to diagnose a patient? Read the text aloud Show
  1. Dog ears can hear frequencies of sound that are higher than a human can hear. If an animal could see frequencies of light higher than humans can, what spectrum would they be able to see? Read the text aloud Show
  1. Many people have radios in their car. When they listen to them, are they listening to radio waves? Explain. Read the text aloud Show
  1. Calculate the speed of light in crown glass for the following:
    1. violet light (n = 1.532)
    2. red light (n = 1.513)
    Which travels faster through crown glass, violet light or red light? Read the text aloud Show
  1. During a talk show segment a medical guest recommended the use of “safe” UVB (ultraviolet B) tanning beds for getting vitamin D. Vitamin D is important for human health, yet many Americans are deficient in the vitamin. The World Health Organization recommends against using a tanning bed for cosmetic purposes and classifies the beds as “carcinogenic to humans.” Research this issue and evaluate the validity of this doctor’s claims that you should not “believe all the negative hype on tanning beds.” Cite specific evidence for your conclusion. Show

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