Physics Notes: Different Types of Waves & their Properties

Different Types of Waves & their Properties

WAVE

A wave is a disturbance, which propagates energy from one place to the other without the transportation of matter.

Types of Waves:

Mechanical wave (longitudinal wave and transverse wave)
Electromagnetic wave

Mechanical Wave

Longitudinal Waves

In this wave, the particles of the medium vibrate in the direction of propagation of the wave.
Waves on springs or sound waves in air are examples of longitudinal waves.

Transverse Waves

In this wave, the particles of the medium vibrate perpendicular to the direction of propagation of the wave.
Waves on strings under tension, waves on the surface of the water are the examples of transverse waves.

Electromagnetic Waves

The waves, which do not require a medium for their propagation i.e., which can propagate even through the vacuum are called electromagnetic waves.
These waves propagate with the velocity of light in vacuum.
Following are the electromagnetic (Non-mechanical) waves-
1. Gama rays (Highest frequency)
2. X-rays
3. UV rays
4. Visible radiation
5. Infra-red rays
6. Short radio waves
7. Long radio waves (Lowest frequency)
All are in decreasing order of the frequency.
Following waves are not categorized as electromagnetic.
1. Cathode rays
2. Canal rays
3. Alpha rays
4. Beta rays
5. Sound waves
6. Ultrasonic wave

Sound Waves

Sound waves are longitudinal mechanical waves. Based on their frequency range sound waves are divided into the following categories.
(a) The sound waves which lie in the frequency range 20 Hz to 20000 Hz are called audible waves.
(b) The sound waves having frequencies less than 20 Hz are called infrasonic
(c) The sound waves having frequencies greater than 20000 Hz are called ultrasonic waves. Ultrasonic waves are used for sending signals, measuring the depth of see, cleaning clothes and machinery parts, remaining lamp short from the chimney of factories and in ultrasonography.

Speed of Sound

The speed of sound is maximum in solids minimum in gases.
When the sound goes from one medium to another medium, its speed and wavelength change, but the frequency remains unchanged. The speed of sound remains unchanged by the increase or decrease of pressure.
The speed of sound increases with the increase of the temperature of the medium.
The speed of sound is more in humid air than in dry air because the density of humid air is less than the density of dry air.

Echo

The repetition of sound due to the reflection of sound waves is called an echo.

Intensity

It is defined as the amount of energy passing normally per unit area held around that point per source unit time.

Pitch

The sensation of a frequency is commonly referred to as the pitch of a sound.

Sonar

It stands for sound navigation and ranging. It is used to measure the depth of a sea, to locate enemy submarines and shipwrecks.

Doppler's Effect

If there is a relative motion between the source of sound and the observer, the apparent frequency of the sound heard by the observer is different from the actual frequency of sound emitted by the source. this phenomenon is called Doppler's Effect.