Question

Monochromatic light of wavelength 600 nm is incident from the air on a water surface. The refractive index of water is 1.33. Find the

1. wavelength,
2. frequency and
3. speed, of reflected and refracted light.

Answer 1

Given: λ = 600 nm, µ = 1.33

(i) In reflection, the ray will reflect back in the same medium as that of the incident ray.

Hence, wavelength (λ) = 600 nm

(ii) Frequency = υ = `"c"/λ = (3 xx 10^8)/(600 xx 10^-9)`

= 0.5 × 10¹⁵ Hz

(iii) Speed = 3 × 10⁸ ms⁻¹

In refraction, the speed and wavelength change while the frequency remains the same.

Hence, speed = ν = `"c"/µ = (3 xx 10^8)/(1.33)`

= 2.26 × 10⁸ ms⁻¹

Wavelength = λ = `ν/υ`

= `(2.26 xx 10^8)/(0.5 xx 10^15)`

= 4.52 × 10⁻⁷ m

= 452 nm

Frequency = υ = 0.5 × 10¹⁵ Hz