Example ( Analog Communication )

For a light ray which have the wavelength equal to 200 nm, calculate the frequency of the ray.

Solution: As given, in the problem,

Wavelength of the light ray = 200 nm

$\lambda = 200 \times 10^{-9} m$

Also speed of light,

C = $3 × 10^8 m s{-1}$

Substituting these values in the equation above, we get that,

$\lambda = \frac {c}{f}$

Rearranging the formula,

f = $\frac {c}{\lambda}$

= $\frac {3\times 10^8}{200 \times 10^{-9}}$

= $1.5 \times 10^{14} Hz.$

The frequency of the wave is equal to $1.5 \times 10^{14} Hz.$