XDD asked in 科學其他:科學 · 1 decade ago

Refraction & Lens

A beam of light in air strikes a slab of glass (n=1.52) and is partially reflected. Find the

angle of incidence if the angle of reflection is twice the angle of refraction.

An 80-mm-focal-local-length lens is used to focus an image on the film of a camere. The

maximum distance allowed between the lens and the film plane is 120mm. What is the

closest object this length could photoraph sharply?

Update:

呃,抱歉這麼說

但第二題的答案好像應該是大於等於什麼吧?

Update 2:

喔對不起

是我弄錯了><

1 Answer

Rating
  • 1 decade ago
    Favorite Answer

    1. In fact, the angle of reflection equals the angle of incidence.

    By Snell's law,

    n1sin@1 = n2sin@2

    (1.0003)sin@1 = 1.52sin(@1/2)

    2sin(@1/2)cos(@1/2) = (1.52/1.0003)sin(@1/2)

    cos(@1/2) = 0.75977

    Angle of incidence, @1 = 81.1*

    2. Focal length, f = 80 mm

    Image distance, v = 120 mm

    By lens formula,

    1/f = 1/u + 1/v

    1/80 = 1/u + 1/120

    Object distance, u = 240 mm

    Source(s): Physics king
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