CHAPTERS 14, 15, 16 EM WAVES & LIGHT TEST REVIEW

-ANSWERS-

  1. What type of wave is an electromagnetic wave?

Transverse

  1. List the different classifications of Electromagnetic Waves in order.

radio, microwave, infrared, visible light, ultraviolet, x-ray, gamma ray

  1. List examples of each classification of EM wave.

radio: radio, television

microwave: radar, microwave ovens

infrared: infrared photography, physical therapy

visible light: photography, astronomy

ultraviolet: sterilization of medical instruments

x-ray: medical x-rays

gamma ray: examination for structural flaws, cancer treatment

  1. What is the speed of electromagnetic waves in a vacuum?

c = 3.0 x 108 m/s

  1. If you know the frequency of electromagnetic radiation, how would you determine the wavelength?

Divide the speed of light by the frequency (v = fλ)

  1. What is the wavelength of gamma rays with a frequency of 3.0 x 1021 Hz?

λ = c/f = 3.0 x 108 / 3.0 x 1021

1.0 x 10-13 m

  1. What s the frequency of an electromagnetic wave is it has a wavelength of 1.0 km?

f = c/ λ = 3.0 x 108 / 1000

3.0 x 105 Hz

  1. What is the frequency of ultraviolet radiation that has a wavelength of 125 nm?

f = c/ λ = 3.0 x 108 / 125 x 10-9

2.4 x 1015 Hz

  1. Compare the wavelength, frequency and speed of two different colors of light.

Color / Wavelength / Frequency / Speed
Red / Longer / Lower / Same
Violet / Shorter / Higher / Same
  1. How can you block all light with polarized lenses?

By rotating the lenses 90 degrees to each other

  1. Refraction occurs when a wave moves between two different ______.

Mediums

  1. Describe the effects of refraction on how something looks when it is underwater.

Its shape and size look different

  1. Of the following properties of light: speed, frequency and wavelength; which change and which stay the same when light is refracted?

Speed and wavelength change, frequency does not

  1. When light moves into a material in which it slows down, which direction does the light bend?

Towards normal

  1. When light moves from air into water, which direction does the light bend?

Towards normal

  1. When light moves from a medium with an index of refraction of 1.5 to a medium with index of refraction of 1.2, which direction does the light bend?

Away from normal

  1. Light passes from air into water (n=1.33). If the angle of incidence is 25 degrees, what is the angle of refraction?

ni sinθi = nr sinθr

1 sin 25 = 1.33 sinθr

sin-1[(1 sin 25) / 1.33] = θr = 19 degrees

  1. Light moves from air into a transparent material. The angle of incidence is 40 degrees and the angle of refraction is 26 degrees. What is the index of refraction for the transparent material?

ni sinθi = nr sinθr

1 sin 40 = nr sin 26

(1 sin 40) / sin 26 = nr = 1.5

  1. What is coherence?

Waves that have the same wavelength and constant phase relationship

  1. To create an interference pattern from two sources, what conditions need to be met by the sources?

Coherent and monochromatic

  1. When does diffraction occur?

When a wave encounters an obstacle, opening, or sharp edge

  1. When a diffraction pattern appears, what causes the bright spots? The dark spots?

Bright spots will occur when you have constructive interference such as two crests or two troughs overlapping. Dark spots will occur when you have destructive interference such as a crest overlapping with a trough.

  1. Is laser light coherent? Monochromatic?

Yes and yes

  1. What does the acronym laser stand for?

Light Amplification by Stimulated Emission of Radiation

  1. What are some uses of lasers?

Treat glaucoma, measure distances, read bar codes, read data on CDs and DVDs, scar removal