video lecture for sound
Question 1: In the curve half the wavelength is
(a) `AB`
(b) `BD`
(c) `DE`
(d) `AE`
Question 2: Thegiven graph shows the displacement versus time relation for a disturbance travelling with velocity of `1500 m s^{-1}`. Calculate the wavelength of the disturbance.
Question 3: Establish the relationship between speed of sound, its wavelength and frequency. If velocity of sound in air is `340 ms^{-1}`, calculate
(i) wavelength when frequency is `256 Hz`.
(ii) frequency when wavelength is `0.85 m`.
Question 4: The frequency of a sound wave in a given medium is `220 Hz` and the velocity is `440 ms^{-1}`. Calculating the wavelength of this wave.
a) `2m`
b) `3m`
c) `1m`
d) `0m`
Question 5: The average hearing range of a person is `20 Hz` to `20 KHz`. Find the wavelength of the sound waves for these two frequencies. Take the velocity of sound in air to be `344 ms^{-1}`.
a) `0.0172 m`
b) `172 m`
c) `0.172 m`
d) `344 m`
Question 6: The frequency of a sound source is `100 Hz`. How many times will it vibrate in a minute?
a) `100` times
b) `60` times
c) `6000` times
d) `600` times
Question 7: A sound wave travels at a speed of `339 ms^{-1}`. If its wavelength is `1.5 cm`, then what will be the frequency of the wave? Will it be audible?
a) `22600 Hz`, These will not be audible.
b) `22600 Hz`, These will be audible.
c) `22300 Hz`, These will not be audible.
d) `22100 Hz`, These will be audible.
Question 8: Why are sound waves called mechanical waves?
Answer Key
Q1: Solution:
(b) `BD` represents half the wavelength in the curve.
Q2: Solution:
From the given graph,
Time period of the disturbance,
`T = 2 µ s = 2\times10^{-6}s`
Velocity of disturbance, `v = 1500 m s^{-1}` So, wavelength of the disturbance,
`λ = vT`
`= 1500 m s^{-1}\times2\times10^{-6} s = 3\times10^{-3} m`
Q3: Solution:
Speed of sound is the distance travelled by sound wave per unit time.
Distance travelled by sound wave in periodic time (`T`) = wavelength (`λ`) of the sound wave.
Thus, speed of sound `v =` distance(`λ`)/time`(T)`
`v=T`
Frequency, `u=1T`
thus `v = u`
Velocity of sound in air, `v = 340 m s^{-1}`
(i) Frequency, `u = 256 Hz`
∴ Wavelength, `λ = v/υ = 340/ 256 m = 1.33M.`
(ii) Wavelength, `λ = 0.85 m`
∴ Frequency `v =v/λ = 340/ 0.85Hz = 400Hz`
Q4: (a), Q5: (a), Q6: (C), Q7: (a)
Q8: Answer: Sound is an energy that cannot be generated by itself. Some sort of mechanical energy is required to produce it. Whether we clap or ring a bell with a hammer - mechanical energy generates sound energy which moves in the form of waves that's why sound waves are called mechanical waves.
Comments
Post a Comment