Question

Calculate the wavelength, frequency and wave number of a light wave whose period is $2.0×10^{–10}\ s$.

Answer 1

Frequency of light:
$ν = \frac {1}{\text P{eriod}}$

$ν = \frac {1}{2.0×10^{-10} \ s}$
$ν = 5.0×10^9 \ s^{-1}$
Wavelength of light $λ = \frac cv$
Where,
c = velocity of light in vacuum = $3×10^8\ m/s$
Substituting the value in the given expression of λ:
$λ = \frac {3×10^8}{5.0×10^9}$
$λ = 6.0×10^{-2}\ m$
Wave number of light:
$\bar ν = \frac 1λ$
$\bar ν=\frac {1}{6.0×10^{-2}}$
$\bar ν= 1.66 × 10^1\ m^{-1}$
$\bar ν= 16.66 \ m^{-1}$