Relation Between Frequency And Wavelength

Electromagnetic Radiation

What is Frequency?

Frequency is defined as the number of oscillations of a wave per unit time being measured in hertz(Hz). The frequency is directly proportional to the pitch. Humans can hear sounds with frequencies ranging between 20 – 20000 Hz. Sounds with frequencies over the human ears range are known as ultrasound and sounds with frequencies less than the audible range is known as infra sound.

You need to know what does Wavelength and frequency mean to understand the relationship among them.

What is Wavelength?

All points on a wave oscillate, i.e, all points on a wave exhibit a type of regular change in a particular value. For instance, when you make a wave by wiggling up and down, the rope molecules repeatedly move up and down. When you consider electromagnetic wave, the value of magnetic and electric fields keep changing because of the wave at a point. If the wave is not a short pulse, the value of electric and magnetic fields keep changing at any point. For example, two points on a wave which attain their maximum value oscillates simultaneously in unison.

Wavelength is defined as the distance between two most near points in phase with each other. Hence, two adjacent peaks or troughs on a wave are separated by a distance of single complete wavelength. Mostly, we use the letter lambda () to describe the wavelength of a wave.

Relation between Frequency and Wavelength

You can treat a wave with higher frequency on a rope faster than before. During this, you notice that the wavelength become shorter. Therefore, the relation between frequency and wavelength do exist, so let’s find out what exactly is this relationship.

Another quantity is Period (T) that can be used to describe a wave. It is defined as the time taken to complete oscillation. Because frequency determines the number of times a wave oscillates and it can be expressed as,
f = 1 / t

Every point on the wave returns to the same value after one period, since a wave undergoes one oscillation during one period. This occurs as a result of every session of oscillation travelling a distance of a wavelength in one period to finish.

The wave speed (v) is defined as the distance traveled by a wave per unit time. If considered that the wave travels a distance of one wavelength in one period,

ν=λ/T

As we know that T = 1/f, hence we can express the above equation as,

V = f λ

The wave speed is equal to the product of its frequency and wavelength, and this implies the relationship between frequency and wavelength.


Practise This Question

Identify the correct sequence of events that take place when an external force acts on a block (at rest) kept on a rough surface.

A. The block starts moving.
B. Static friction starts acting on the block.
C. Kinetic friction acts on the block.
D. The block continues to be stationary.