In the reflected light the wavelength and frequency remain the same as that of incident light. Wavelength of reflected light = 5000 Å, frequency of reflected light c = f λ f = $\frac{c}{\lambda}$ = $\frac{3 \times 10^8}{5 \times 10^{-7}}$ = 6 × $10^{14}$ Hz when reflected ray is normal to incident ray, ∠i + ∠r = 90° 2∠i = 90° (∴ ∠i = ∠r) ∠i = 45° For an angle of incidence 45° the reflected ray is normal to incident ray.