Question

The frequency of a light wave in a material is 4 × 10¹⁴ Hz and wavelength is 5000 Å . The refractive index of material will be _______ ( take c = 3 × 10⁸ ms^–1) 

(A) 1.5 (B) 1.7 (C) 1.33 (D) None of these

Answer 1

The correct option is (A) 1.5.

Explanation:

 λ = 5000 A° = 5000 × 10^–10 m

f = 4 × 10¹⁴ Hz

hence  v = fλ

 v = 4 × 10¹⁴ × 5000 × 10^–10 = 20 × 10⁷ m/s

η = (c/v)

η = [(3 × 10⁸) / (2 × 10⁸)] = 1.5