22. The frequency of a light wave in a material is 2 × 10¹⁴ Hz and wavelength is 5000A ̊ . The refractive index of material will be ?

22. The frequency of a light wave in a material is 2 × 10¹⁴ Hz and wavelength is 5000A ̊ . The refractive index of material will be ?

(a) 1.50

(b) 3.00

(c) 1.33

(d) 1.40

Answer :  (b) 3.00

\( v = \nu \lambda \)

\( v = (2 \times 10^{14}) \times (5 \times 10^{-7}) = 1 \times 10^8 \, \text{m/s} \)

\( \mu = \frac{c}{v} = \frac{3 \times 10^8}{1 \times 10^8} = 3 \)