Ncert Exercises & Solutions

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

= \frac{1}{2.0 x 10^{- 10}} = 5.0 x 10^{9} s^{- 1}

Wavelength

(λ)

of light = c/v
Where,
c = velocity of light in vacuum = 3 ×

10^{8}

m/s
Substituting the value in the given expression of λ:

λ = \frac{3 \times 10^{8}}{5.0 \times 10^{9}} = 6.0 \times 10^{- 2} m

Wavelength (

\vec{v}

) of light =

\frac{1}{λ} = \frac{1}{6.0 x 10^{- 2}} = 1.66 x 10^{1} m^{- 1} = 16.66 m