MHT-CET Physics Crash Course “Harmonics and Overtones” Class 12

“Harmonics and Overtones” MHT-CET Class 12 Physics Crash Course | Chapter – Superposition of Waves

In this session G.S. Khairnar discussed the theory and MCQ’s of “Harmonics and Overtones”. The session will be useful for all the aspirants of MHT-CET 2022. The session will be in Marathi and English.

Harmonics and Overtones:-

Hello dear students in this article we are going to study about the different frequencies that are obtained in modes of vibrations of air column in pipe, stretched string etc.

Number of vibrations performed by particle per unit time is called as frequency of vibration. SI unit of frequency is Hz.

Time required to complete one vibration is called as period of vibration. SI unit of period is second.

Let’s discuss about harmonics and overtones in detail….!

We know that the there is restriction of boundary conditions for formation of stationary waves of particular frequency or wavelength. When stationary waves are formed with the help of stretched string or air column in pipe some natural frequencies are formed with normal modes of vibrations.

The minimum frequency that formed are known as fundamental frequency and the corresponding mode of vibration is knows as fundamental mode of vibration.

The minimum frequency is also known as first harmonic.

• Harmonics:-

The integral multiple of fundamental frequency including fundamental frequency are called harmonics.

The lowest possible frequency is called as fundamental frequency or 1st harmonic.

E.g. If the minimum frequency formed in any case is 100 Hz. Then n=100 Hz is known as fundamental frequency or 1st harmonic. Then the next integral multiples of frequencies are termed as 2nd harmonic, 3rd harmonic and so on. i.e. n’= 200 Hz in this case will be termed as 2nd harmonic.

In case of modes of vibrations of stretched string and pipe open at both ends, all harmonics i.e. even as well as odd harmonics are present. Whereas in case of pipe closed at one end, only odd harmonics are present. In some cases all harmonics may or may not be present.

• Overtone:-

The integral multiple of fundamental frequency, excluding the fundamental frequency which are actually present are called overtones.

Overtones are the used to describe higher frequencies which come after fundamental frequency.

The first frequency higher that fundamental frequency is termed as first overtone, next higher frequency is second overtone and so on.

Eg 1. Consider the case of vibrations of stretched string, in which the harmonics and overtones can be given as below,

Eg 2. Consider the case of vibrations of air columns in pipe closed at one end, in which the harmonics and overtones can be given as below,

Let’s solve the following MCQ’s………….!

Q.1) The vibrations of object under external periodic frequencies are known as……

a) free vibrations

b) damped vibrations

c) forced vibrations

d) none of these

c) forced vibrations

Q.2) Stethoscope used in medical diagnosis is working on principle of ……..which is special case of forced vibrations.

a) damping

b) resonance

c) superposition

d) none of these

b) resonance

Q.3) The minimum frequency that can be formed in modes of vibrations of object is known as…….

a) damping frequency

b) resonating frequency

c) fundamental frequency

d) natural frequency

c) fundamental frequency

Q.4) The frequencies which are integral multiple of fundamental frequencies including fundamental frequencies are called as…….

a) harmonics

b) overtones

c) either ‘a’ or ‘b’

d) neither ‘a’ nor ‘b’

a) harmonics

Q.5) Higher frequencies which are integral multiple of fundamental frequencies excluding fundamental frequencies are called as…….

a) harmonics

b) overtones

c) either ‘a’ or ‘b’

d) neither ‘a’ nor ‘b’

b) overtones

Q.6) In case of modes of vibrations of air column in pipe closed at one end…….

a) all harmonics are present

b) only even harmonics are present

c) only odd harmonics are present

d) none of these

c) only odd harmonics are present

Q.7) In case of modes of vibrations of air column in pipe closed at one end…….

a) Nth overtone= (n+1)th harmonic

b) Nth overtone= (2n+1)th harmonic

c) Nth overtone= (n-1)th harmonic

d) Nth overtone= (2n-1)th harmonic

b) Nth overtone= (2n+1)th harmonic

♦जिल्हा नुसार जाहिराती ♦

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