Speed, frequency, wavelength for 9th class (lec 3)

 video lecture for Speed, frequency, wavelength

Question 1:  Arrange the three states of matter in the decreasing order of velocity of sound in them.

Question 2:  On what factors, does the velocity of sound in a medium, depend?

Question 3: Explain the factors on which the velocity of sound in a gas depends.

Question 4:  Explain the factors on which the velocity of sound in the air does not depend.

Question 5: The velocity of sound in solids is affected by their density.

Question 6: Earthquake produces which kind of sound before the main shockwave begins

(a) ultrasound

(b) infrasound

(c) audible sound

(d) none of the above

Question 7: In which medium, air, water, or iron, does sound travel fastest?

Question 8: What is the reason that the voice of women is thin and that of men is thick? 

Answer Key

Q1: Sound travels fastest in solids, then in liquids, and the slowest in gases.

Q2: Hence, the speed of sound in a median depends upon the density of the medium, elasticity of the medium, temperature, and pressure of the medium.

Q3:  The speed of sound in a gas depends on the density and elasticity of the gas.

Q4: The speed of sound does not depend on the pressure.

Q5:  True

Q6: Solution:

(b) Earthquake produces infrasound before the main shock wave begins.

Q7:  Sound travels faster through iron than air and water. The speed of sound in iron is `5950 ms^{-1}`.

Q8:  The thickness or thinness of the sound depends on the pitch of the sound because the pitch of the voice of women is high, hence the voice is thin. On the contrary, the pitch of the voice of men is low, hence the voice is thick.