Question 9

Light of wavelength 5000 Å falls on a plane reflecting surface. What are the wavelength and frequency of the reflected light? For what angle of incidence is the reflected ray normal to the incident ray?

Answer

It is given that,

Wavelength of incident light, λ = 5000 Å = 5000 × 10 ^{-10} m

We know that, Speed of light, c = 3 × 10^{ 8} m

Frequency of incident light is given by the relation, *v = c/λ* = 3x10^{8}/5000x10^{-10} = 6x10^{14} Hz

The wavelength and frequency of incident light is the same as that of reflected ray. Hence, the wavelength of reflected light is 5000 Å and its frequency is 6 × 10^{ 14 }Hz. When reflected ray is normal to incident ray, the sum of the angle of incidence, ang. i and angle of reflection, ang. r is 90°.

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