physicsa.com
class code: SPS21 teacher: Mr. Elert
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Physics A: Problem Set 17: Reflection

recommended reading

High Marks: 4:36–4:40
Barron's Let's Review: 11.5 Reflection, 12.5 Reflection
physics.info: Reflection
Wikipedia: Reflection (physics)
HyperPhysics: Reflection
Khan Academy: Reflection and refraction
Reference table with select items highlighted, page 1 Reference table with select items highlighted, page 2 Reference table with select items highlighted, page 3 Reference table with select items highlighted, page 4 Reference table with select items highlighted, page 5 Reference table with select items highlighted, page 6

in class

  1. caroms.pdf
    The diagram below shows two mirrors that meet at a right angle. Several rays of light enter from above and strike the mirror on the left. Draw the path of one ray as it reflects first off the left mirror and then off the lower mirror.

    2 plane mirrors at a right angle. 9 rays of light incident at various angles upon a point on one of them.

    1. What numbered point does the ray pass through as it leaves the diagram?
    2. How does the direction of the ray entering the diagram compare to the direction of the ray that left the diagram?

    Here are all the resulting rays — color coded for your enjoyment.

    All 9 results, color coded

    1. The number that the exiting ray will pass through is double the number that the entering ray did pass through — enter on 4, exit on 8; enter on 12, exit on 24.
    2. The ray exiting the diagram is parallel (antiparallel, actually) to the entering ray.
  2. Why is the lettering on the front of some vehicles backward? Why is the lettering on the back and sides of these vehicles not also backward?

    The lettering on the front of emergency vehicles is backward so that it looks correct when viewed in a mirror. This is so that drivers will be able to react more quickly to emergency vehicles that are behind them and yield the right of way. The lettering on back and sides is not written backward since these surfaces are normally viewed when the emergency vehicle is ahead of or along side the driver.