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Physics 121 - Reflection Question

da_prodigy
edited February 2008 in General
Can someone help me with this question? It seems so easy but I haven't taken physics in a couple years, so I'm kind of rusty.

reflectionvo4.png

Q: A light ray leaves point A, reflects from the mirror, and reaches point B. How far below the top edge does the ray strike the mirror.

So basically, a line is drawn from A to the mirror, reflecting to B. Angle of incidence will be equal to angle of reflection of course, but where do we go from there?

Comments

  • Jimmy
    edited February 2008
    since no one is helping you ill take a stab at it, but im a little rusty on physics

    Stay tuned for pucture
  • Jimmy
    edited February 2008
    reflectionvo4.png

    hope this helps, i kinda forgot all the formulas but i hope this points u in the right direction
  • Simon604
    edited February 2008
    This is pretty straightforward, if I can remember correctly from first year.

    answerhf1.png

    Tanθ1 = X1/10

    Tanθ2 = X2/15

    Then, since θ1 = θ2 (interior angles)

    X1/10 = X2/15

    Plug in X2 = 10 – X1 (as per the drawing) and solve

    Answer should be 4m, which you add to the 5m above point A to get 9m
  • da_prodigy
    edited February 2008
    Thank you! It totally makes sense now

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