As we know that sounds propagate through waves, also food can be cooked in the oven by the EM waves. So, can we cook the food just by playing a sound speaker? This is not possible. But why? Although both are waves and propagate the energy, both have different properties so different uses. Sound wave is a mechanical wave and the wave used in the oven is a microwave which is an electromagnetic wave. Similarly we have different kinds of waves which have their different properties and uses. Let's see the different types of waves !
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Wave is a propagation of energy and momentum with or without the use of a medium from one place to another place. The energy can propagate in any form of the elastic deformation of a particle of medium, variation in pressure, electric and magnetic field intensity etc. We can represent a wave as shown in the figure.
Now let's discuss the types of waves.
We have to deal with various waves in our daily life such as string waves, sound waves, radio waves etc., based on the medium waves can be classified as -
Based on the particle motion waves can be classified as
Based on the propagation in space waves can be classified as
A wave that needs a medium to propagate is called a mechanical wave. The medium has the elastic and inertial properties. When a disturbance is produced in the medium due to inertial and elastic properties of the medium, this disturbance propagates in the medium.
Examples of mechanical waves are as follows :
The mechanical wave further can be classified into two parts as transverse and longitudinal waves.
In an electromagnetic wave the electric field and magnetic field oscillate perpendicular to the direction of wave motion. Magnetic field and electric field are mutually perpendicular.
The examples where electromagnetic waves are involved are as follows-
In the increasing order of the wavelength the electromagnetic waves are
A french physicist De broglie gave the concept of the dual nature of matter. According to which, when a matter particle moves with a larger velocity it behaves as a wave.The wavelength of matter wave is called de broglie wavelength, and is given by
Where h= planck’s constant = 6.62 × 10-34m2 kg/s
p = momentum of particle
m = mass of particle
v = velocity of particle
However it is difficult to observe this phenomena in day-to -day life. But it can be seen in various physical experiments like, a beam of electrons shows diffraction just like the beam of light which is an electromagnetic wave.
Q1. What is the wavelength of a wave shown in the figure ?
A. In figure the 2 waves having the length 12 m
Hence wavelength of the wave is 6 m
Q2. The time period of a wave is 0.2 s, then what is the frequency of the wave?
A. Given the time period of wave is T=0.2 s
We know the relation of frequency with time period
Q3. An electron is moving with the velocity 1.6 106 m/s, find the wavelength associated with electrons. Mass of an electron is 9.1 10-31 and planck’s constant is 6.62 × 10-34m2 kg/s .
A. Given Planck’s constant h = 6.62 × 10-34m2 kg / s
Mass of the electron m=9.1×10-31
Velocity of electron v=1.6×106 m/s
The wavelength of a matter wave is given by
Q4. Write the difference between the transverse waves and longitudinal waves.
A. We can differentiate the transverse waves and longitudinal waves as
The oscillation of a particle is perpendicular to the direction of wave propagation.
The oscillation is in the same direction as that of the wave propagation
This wave propagates in the form of crests and troughs.
The propagation of waves takes as rarefaction and compression.
Examples of transverse waves are string waves, light waves etc.
Examples of longitudinal waves are sound waves, p-type waves of earthquakes etc.
Q1. Velocity of a mechanical wave depends on?
A. Properties of the medium of propagation define the velocity of a wave.
Q2. Which type of wave is a Sound wave?
A. Sound wave is a longitudinal wave.
Q3. On what factor does the frequency of waves depend?
A. Frequency of wave depends on the source of the wave.
Q4. What are the different colors of visible light?
A. In the increased order of wavelength, the colors are Violet, Indigo, Blue, Green, Yellow, Orange, Red.