2.7 Calculate the wavelength, frequency, and wavenumber of a light wave whose period is 2.0 × 10–10 s.

Frequency (ν) of light = 1/Period
= 12.0 x 10-10 = 5.0 x 109 s-1
Wavelength λ of light = c/v
Where,
c = velocity of light in vacuum = 3 × 108 m/s
Substituting the value in the given expression of λ:
λ = 3 × 1085.0 × 109 = 6.0 × 10-2 m
Wavelength (v) of light = 1λ = 16.0 x 10-2 = 1.66 x 101 m-1 = 16.66 m