Question

The frequency of a wave is $6\times 10^{15}{s}^{-1}$ Its wave number would be

• A. $10^{5}c{m}^{-1}$
• B. $2\times 10^7{m}^{-1}$
• C. $2\times 10^{7}c{m}^{-1}$
• D. $2\times 10^{5}c{m}^{-1}$

Answer 1

Answer: (B)

Wave number $(\bar{v})=\frac{1}{\text{ Wavelength }(\lambda )}=\frac{\text{ Velocity (c)}}{\text{Frequency}(v)}$
$c=v\lambda$
$v=\frac{c}{\lambda }$
$v=c\times \bar{v}$
$\overline{v}=\frac{v}{c}$
$\therefore \bar{v}=\frac{6\times 10^{15}{s}^{-1}}{3.0\times 10^{8}m/s}$
$=2\times 10^{7m^{-1}}$