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Gary
Lv 4
Gary asked in Science & MathematicsPhysics · 10 years ago

Physics question... refraction of light at a plane surface?

an equilateral prism of glass of refrqctive index 1.45 is immersed in water of refractive index 1.33 A narrow beam of light falls normally on one face of the prism. what is the angle of emergence????

taken from isc nootan physics

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  • 10 years ago
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    There are two angles of emergence, one is the wave refracting off the glass from the water and the second is from the glass back to the water.

    n2/n1 = sin i / sin r

    where n2 is the refractive index of the second medium

    n1 is the refractive index of the first medium

    i = angle of incidence (degrees)

    r = angle of emergence (or refraction)

    Also by using your rules inside the prism, you will find the angle of incidence is 60 degrees. Each angle of the triangle corners is 60 degrees also.

    1.45/1.33 = sin 60/sin r

    sin60 x 1.33/1.45 = 0.79 = sin r

    sin^-1 (-0.28) = r

    r = 52.6 degrees

    Okay so now the light is inside the glass prism. I also worked out that the next angle of incidence to be 37.4 degrees.

    Therefore:

    sin 37.4/sin r = 1.33/1.45

    sin r = sin37.4 x 1.45/1.33

    sin r = 0.66

    r = sin^-1 (0.66)

    = 41.66 degrees

    Therefore the light emerges from the prism at an angle of 41.66 degrees.

    Am I right?

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