Section 1 review
Refraction of light occurs at the boundary between two different media, such as between glass and air. In refraction, a light ray is bent toward the normal if it passes into a material with a higher index of refraction and away from the normal if the second material has a lower index. A greater difference between the indices of refraction of the two materials causes light to bend more. When light passes from a higher index material (such as water) to a lower index material (such as air), there is a critical angle of incidence. At angles of incidence greater than the critical angle, a light ray is totally reflected back into the incident medium and there is no refracted ray. This is called total internal reflection. Read the text aloud
refraction, index of refraction, Snell’s law of refraction, critical angle, total internal reflection

n i sin θ i = n r sin θ r
sin θ c = n r n i

Review problems and questions

  1. Light from air enters a piece of amber (n = 1.55) on a necklace at an angle of 45°. What is the angle of refraction of the light inside the amber? Read the text aloud Show
  1. Light passing through glass is completely internally reflected when it hits the glass–air barrier at an angle of incidence of 40.0°. What kind(s) of glass could this possibly be? Use the table of indices of refraction to identify different types of glass. Read the text aloud Show
  1. Eddie goes into a jewelry store to sell a large diamond cube that has been in the family for generations. The jeweler needs to test the cube to confirm that it is really diamond, but she cannot hit it with a hammer because she might break it. So she tests the block’s ability to refract light. She shines a laser into the block at various angles and measures the refracted angle. Her data are in the table to the right.
    1. What is the index of refraction for this block?
    2. What material is this block made out of?
    3. Using optics, is there a different way to test whether the cube is diamond?
  
θiθr
30.0°19.6°
45.0°28.3°
60.0°35.5°
Read the text aloud Show
  1. A physicist has three materials (A, B, and C) with indices of refraction 1, 2, and 3, respectively.
    1. Does a light ray shining from A into B deflect away from or toward the normal?
    2. Does a light ray shining from C into B deflect away from or toward the normal?
    3. Does a light ray shining from A into C deflect away from or toward the normal?
    4. If the angle of incidence is always 30°, does the light ray deflect more in a or in c? Read the text aloud Show

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