Question

Yellow light emitted from a sodium lamp has a wavelength (λ) of 580 nm. Calculate the frequency (ν) and wavenumber (v) of the yellow light

Answer 1

From the expression, \(λ = \frac {c}{v}\)
We get,
\(v = \frac {c}{λ}\)      ......(i)
Where, 
 ν = frequency of yellow light 
c = velocity of light in vacuum = 3 × 10⁸ m/s
λ = wavelength of yellow light = 580 nm = 580 × 10^-9 m
Substituting the values in expression (i):
\(v = \frac {3×10^8}{580×10^{-9}}\)
\(v = 5.17×10^{-14} s^{-1}\)
Thus, frequency of yellow light emitted from the sodium lamp
= \(5.17×10^{14} s^{-1}\)
Wave number of yellow light,
\(\bar v= \frac 1λ\)
\(\bar v= \frac {1}{580×10^{-9}}\)
\(\bar v= 1.72×10^6\  m^{-1}\)