Question

Yellow light emitted from a sodium lamp has a wavelength (λ) of 580 nm. Calculate the frequency (ν) and wave number ( $\overline{V}$ ) of the yellow light.

Answer 1

From the expression,
$\lambda =\frac{c}{v}weget,v=\frac{c}{\lambda }.............\left(i\right)$
Where, ν = frequency of yellow light
c = velocity of light in vacuum = 3 × ${10}^8$ m/s
λ = wavelength of yellow light = 580 nm = 580 × ${10}^{–9}$ m Substituting the values in expression (i):
$v=\frac{3\times {10}^8}{580\times {10}^{-9}}=5.17\times {10}^{14}{s}^{-1}$
Thus, frequency of yellow light emitted from the sodium lamp = 5.17 × ${10}^{14}{s}^{–1}$
Wave number of yellow light $\overline{v}=\frac{1}{\lambda },=\frac{1}{580\times {10}^{-9}}=1.72\times {10}^6{m}^{-1}$