Question

A visible violet light emits light with a wavelength of 4.00 × 10-7 m. Calculate the frequency of the violet light.

Answer 1

For any wave,             
                           Frequency = (speed) / (wavelength)

                                              = (3 x 10⁸ m/s) / (4 x 10⁻⁷ m)

                                              = (3/4 x 10¹⁵)  ( m / m - s )

                                              = (0.75 x 10¹⁵)  /sec

                                              =  7.5 x 10¹⁴  Hz

                                              =   750,000 GHz 

                  

Answer 2

Answer: The correct answer is $f=75\times 10^{13}$ Hz.

Explanation:

The expression of the wavelength in terms of the frequency is as follows;

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

Here, c is the speed of the light, f is the frequency of the wave and $\lambda$ is the wavelength of the wave.

It is given in the problem that a visible violet light emits light with a wavelength of 4.00 × 10-7 m.

Calculate the frequency of the violet light by rearranging the above expression.

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

Put $c=3\times 10^{8} m/s$ and ${\lambda }=4\times 10^{-7}$.

$f=\frac{3\times 10^{8}}{4\times 10^{-7}}$

$f=75\times 10^{13} Hz$

Therefore, the frequency of the violet light is $f=75\times 10^{13} Hz$.