Subject: Physics
A wave is a continuous transfer of disturbance from one part of a medium to another through successive vibrations of particles of the medium about their mean positions. In wave motion, energy and momentum are carried from one region to another region of the medium. If there is no transfer energy, it is not a wave but an oscillation as there is no transfer of energy.
If the wave requires a material medium to carry energy from one point to another point then it is called a mechanical wave. For a mechanical wave, a medium has elastic nature.
If the wave does not require material medium to carry energy from one point is called a non-mechanical wave. Example: X-ray, microwave, electromagnetic wave.
Crest
It is the maximum displacement of the vibrating particle above equilibrium line of mean position.
Trough
It is the maximum displacement of the vibrating particle below the equilibrium line of the mean position. The velocity of a wave is maximum at equilibrium line and minimum at an extreme point.
Wavelength
It is the distance travelled by the wave to complete one oscillation of vibrating particle on the medium. In other words, a distance between two nearest crests or trough is called wavelength. It is denoted by ‘λ’. It’s unit is a meter. Hence, wave velocity is equal to the product of wavelength and frequency.
Wave velocity
The distance travelled by a wave in one second is called wave velocity, denoted by v.
\begin{align*} \text {wave velocity, v} \: &= \frac {\text {distance travelled by wave}\lambda }{\text {time taken, t}}\\ &= \frac {\lambda }{T} = \lambda f \\ \therefore v &= \lambda f \\ \therefore v = \lambda f \\ \end{align*}
Phase
The angular displacement of the wave at any time‘t’ is called phase of the wave. Phase indicates where the wave reaches and in which direction is the wave.
If the vibrating particle of the medium has oscillated perpendicularly to the direction of propagation of the wave is called a transverse wave. Example: wave in a surface of liquid and wave in solid.
To understand the propagation of a transverse wave, suppose nine particles of a medium numbered as 1 to 9 lying at an equal distance at the mean position shown in the figure. When a wave travels from to right, the particles vibrate up and down about their mean positions and the disturbance travel from the 1st particles to a 9th particle.
After T seconds, the particle 1, 5 and 9 are at their mean positions and the wave has reached to particle 9. Particle 1 and 9 are in the same phase. The wave travelled a distance between particles 1 and 9 in the time in which the particle 1 has completed oscillation.
The top point on the wave at the maximum distance from the mean position is called crest, and the point at the maximum distance below the mean position is called trough. Thus in a transverse wave, crests and trough are alternately produced.
Properties of Transverse Waves
Reference
Manu Kumar Khatry, Manoj Kumar Thapa,et al. Principle of Physics. Kathmandu: Ayam publication PVT LTD, 2010.
S.K. Gautam, J.M. Pradhan. A text Book of Physics. Kathmandu: Surya Publication, 2003.
A wave is a continuous transfer of disturbance from one part of a medium to another through successive vibrations of particles of the medium about their mean positions.
If the wave requires a material medium to carry energy from one point to another point then it is called a mechanical wave.
If the wave does not require material medium to carry energy from one point is called a non-mechanical wave.
Crest is the maximum displacement of the vibrating particle above equilibrium line of mean position.
Trough is the maximum displacement of the vibrating particle below the equilibrium line of the mean position.
Wavelength is the distance travelled by the wave to complete one oscillation of vibrating particle on the medium.
The distance travelled by a wave in one second is called wave velocity, denoted by v.
The angular displacement of the wave at any time‘t’ is called phase of the wave.
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