General Waves Properties - Self Assessment Questions And Text Book Exercise

 

General Waves Properties - Self Assessment Questions And Text Book Exercise

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Physics For Class X
Unit 10: General Waves Properties
Self Assessment Questions

Q.1: Distinguish between transverse and longitudinal waves
Ans: Difference Between Transverse Waves And Longitudinal Waves:

S.NO.	Transverse Waves	Longitudinal Waves
1.	In transverse wave, particles of the medium vibrates perpendicular to the direction of propagation of waves.	In longitudinal wave, particles of the medium vibrates parallel to the direction of propagation of waves.
2.	This wave is made up of crests and troughs.	This wave is made up of compressions and rarefactions.
3.	The production of this wave can take place in liquid and gas mediums only.	The production of this wave can take place in any medium - solid, gas, or liquid.
4.	The polarization or alignment of this wave is certainly possible.	The polarization or alignment of this wave does not happen.
5.	This wave acts in two dimensions.	This wave acts in one dimension.
6.	An example of a transverse wave is the light wave.	An example of a longitudinal wave is the sound wave.

Q.2: Wave motion transfers energy without moving matter. Justify this statement with an example.
Ans: Waves are means of energy transfer without transfer of matter:
The wave is a disturbance in a medium that transfer energy from one place to another, but waves can not move matter the entire distance.

Example No.1:
When the calm water surface is disturbed by a stone dropping into it, circular water ripples spread out from the point where the stone hits the water. Similarly the continuous disturbance of the water surface by the blasts of the wind caused by a helicopter hovering above creates water waves that move outwards. If we place a cork on the surface of water. We observed that when the waves reaches the cork, it will move up an down along the motion of water particles by getting energy from waves but remain at its position. Thus the disturbance on the water surface moves outwards, carrying energy, and no water, because after the waves pass, the cork on water remains where it was before the wave was produced.

Example No.2:
A tide can travel many kilometres. The water moves up and down - a disturbance that travels in a wave, transferring energy, not matter. Let's consider the example of a buoy bobbing in the ocean. The buoy is moved up and down by the waves that pass by it but doesn't move directionally across the water. Waves transfer energy but not mass. When particles in water become part of a wave, they start to move up or down. This means that kinetic energy (energy of movement) has been transferred to them. As the particles move further away from their normal position (up towards the wave crest or down towards the trough), they slow down. This means that some of their kinetic energy has been converted into potential energy - the energy of particles in a wave oscillates between kinetic and potential energy.
This activity shows that water waves like other waves transfer energy from one place to another without transferring matter, i.e., water.

Q.3: What is the main difference between mechanical and electromagnetic waves.
Ans: Difference Between Mechanical Waves And Electromagnetic Waves:

S.NO.	Mechanical Waves	Electromagnetic Waves
1.	Mechanical waves are such waves that need a medium for propagation.	Electromagnetic waves are such waves that do not need a medium for propagation.
2.	Mechanical waves are produced by vibratory motion in the respective medium.	Electromagnetic waves are produced by a changing of electric and magnetic fields.
3.	Mechanical waves consist of transverse as well longitudinal waves.	Electromagnetic only comprised of a transverse wave in nature.
4.	Mechanical waves cannot travel through the vacuum.	Electromagnetic waves travel through the vacuum at the speed of 3×108 m/s.
5.	All mechanical waves travel through their media at different speeds depending upon the physical properties of the respective medium.	All electromagnetic waves can travel through transparent media at different speeds depending upon the refractive index of the respective medium.
6.	Sound waves, water waves and seismic waves are some examples of mechanical waves.	Radio waves, microwaves, light waves, U.V waves and infrared waves are some examples of electromagnetic waves.

Q.4: How spherical wavefronts are produced in the ripple tank?

Ans: In a ripple tank, a spherical dipper can produce circular waves. These waves have a circular wavefront. When the rippler is attached with a point has spherical ball and lowered it so that it just touches the surface of the water, circular waves will be produced.

Circular waves can also be produced by dropping a single drop of water into the ripple tank.

Q.5: What is the difference between displacement and amplitude of the wave?
Ans: Difference Between Displacement And Amplitude Of the Wave:
Displacement of a particle on a wave is a distance in a specific direction from its rest/ equilibrium position. It is a vector quantity and may be positive or negative.

While the amplitude of a wave refers to the maximum displacement moved by a point on the medium from its rest or mean position. It is the height of a crest or depth of a trough measured from the rest position. It refers to the scalar or vector quantity depends on field size.

Q.6: Drive the relation between wave, speed and frequency.
Ans: Relation Between Wave speed And Frequency:
The wave is a disturbance in a medium that transfer energy from one place to another. It travels from one place to another and hence has a specific velocity. This called the velocity (Speed) of the wave and is denoted by Velocity = Distance traveled / time taken or

v = S / t

Let us consider for a wave,
If the time taken by the wave to move from one point to another is equal to its time period 'T', then the distance travelled by the wave will be equal to one wavelength = λ
then

The speed of wave can also be written as V = fλ