Question

What is the frequency of the electromagnetic radiation depicted by the wave in the diagram below?

A) 5 Hz

B) 1.5x10¹⁰ Hz

C) 20 Hz

D) 6x10¹⁰ Hz

Electromagnetic Wave amplitude 10 15 /20 distance (mm)

Answer 1

Relation between speed of electromagnetic wave and frequency is given as

$c=\lambda (wavelength) \times frequency$

wavelength $\lambda$ is define as length of complete wave which can be obtained from the figure shown above as total length of one complete wave which comes out to be 20 mm.

As speed of electromagnetic radiation is $c=3 \times 10^8$ m/s

Here, wavelength $\lambda =20 \times 10^{-3}m$

Thus, frequency = $Frequency = \frac{c}{\lambda}=\frac{3 \times 10^8}{20 \times 10^{-3}} =1.5\times 10^{10}Hz$ (Hz = per second)

Answer : B