Question

The wavelength of violet light is about 425 nm (1 nanometer = 1 × 10−9 m). what are the frequency and period of the light waves?

Answer 1

1) Frequency: $7.06\cdot 10^{14} Hz$

The frequency of electromagnetic radiation is given by:

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

where

$c = 3 \cdot 10^8 m/s$ is the speed of light

$\lambda$ is the wavelength

In this case, the wavelength of the radiation is

$\lambda=425 nm=425\cdot 10^{-9} m$

Therefore the frequency is

$f=\frac{3\cdot 10^8 m/s}{425 \cdot 10^{-9} m}=7.06\cdot 10^{14} Hz$

2) Period: $1.42\cdot 10^{-15} s$

The period is equal to the reciprocal of the frequency of the wave:

$T=\frac{1}{f}$

Using the frequency we found previously, $f=7.06\cdot 10^{14} Hz$, we find:

$T=\frac{1}{7.06\cdot 10^{14} Hz}=1.42\cdot 10^{-15} s$