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8. A parallel beam of light of intensity I is incident normally on a plane surface whichabsorbs 50% of the incident light. Thereflected light falls on B which is a perfectreflector, the light reflected by B is againpartly reflected and partly absorbed and thisprocess continues. For all absorption by A,absorption coefficient is 0.5. The pressureexperienced by A due to light is |
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Answer» Explanation:Radiant pressure formula goes like-(i) When light is completely absorbed,(ii) When light is completely reflected, where, = INTENSITY of INCIDENT light = speed of light = absorption coefficient (0.5) = reflection coefficient (1 - a = 0.5)Now, we only have to find radiation pressure on SURFACE A.At FIRST time, For the light which is absorbed, For the light which is reflected, At second time, because intensity halved after first reflection with = 0.5 For the light which is absorbed, For the light which is reflected, And hence so on...Now addition of all the radiation pressure by light absorbed-Now addition of all the radiation pressure by light reflected-Hence,Total radiation pressure, |
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