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a) A beam of light is incident from air on the surface of aliquid. If the angle

ID: 1667797 • Letter: A

Question

a)
A beam of light is incident from air on the surface of aliquid. If the angle of incidence is 40.0° and the angle ofrefraction is 31.0°, find the critical angle for the liquidwhen surrounded by air.
1° b) A light ray, traveling in air, strikes the surface of abeaker of mineral oil at an angle of 37.5o with thenormal to the surface. The speed of light in mineral oil is 2.17 x108 m/s.. Calculate the angle of refraction.
1o

a)
A beam of light is incident from air on the surface of aliquid. If the angle of incidence is 40.0° and the angle ofrefraction is 31.0°, find the critical angle for the liquidwhen surrounded by air.
1° b) A light ray, traveling in air, strikes the surface of abeaker of mineral oil at an angle of 37.5o with thenormal to the surface. The speed of light in mineral oil is 2.17 x108 m/s.. Calculate the angle of refraction.
1o

Explanation / Answer

Angle of incidence I = 40 degrees

Angle of refraction r= 31 degrees

From Snell’s law index of refraction of theliquid n = sin I / sin r

                          n= 1.248

So, critical angle C = sin -1 ( 1/ n)

                               = 53.25 degrees

(b). Angle of incidence I = 37.5 degrees

Speed of light in mineral v = 2.17 * 10 ^ 8 m / s

Speed of light in vaccum c = 3 * 10 ^ 8 m / s

Index of refraction of mineral n ‘ = c / v

                                                     = 1.382

We know n ‘ = sin I / sin r

From this sin r = sin I / n ‘

                         = sin 37.5 / 1.382

                          = 0.4403

So, angle of refraction r = 26.12 degrees