The Total solution for NCERT class 6-12
Light of wavelength 5000 Å fallson a plane reflecting surface. What are the wavelength and frequency of thereflected light? For what angle of incidence is the reflected ray normal to theincident ray?
Wavelength of incident light, λ =5000 Å = 5000 × 10−10 m
Speed oflight, c = 3 × 108 m
The wavelength and frequency ofincident light is the same as that of reflected ray. Hence, the wavelength ofreflected light is 5000 Å and its frequency is 6 × 1014 Hz.
Whenreflected ray is normal to incident ray, the sum of the angle ofincidence, and angle ofreflection, is 90°.
Accordingto the law of reflection, the angle of incidence is always equal to the angleof reflection. Hence, we can write the sum as:
Therefore, the angle of incidencefor the given condition is 45°.