# Mechanical Waves | Old is Gold | Class XII

__Mechanical Waves__

**Short**

1. Why sound made/produced at a distance can be heard distinctly at night than in the day time?

2. Is velocity of sound more in damp air or in dry day?

3.Why sounds are heard better on a wet day than on a dry day?

4. Do sound waves need a medium to travel from one point to other point in space? What properties of the medium are relevant?

5. Although the density of solid is high, the velocity of sound is great in solid, explain.

6. Explain why the velocity of sound in solids is greater than that in gases, though the densities of solids are greater than that of gases.

7. Sound at distances can be heard distinctly at night than in the day time. Why?

8. Velocity of sound increases on a cloudy day. Why?

9. Sound travels faster in metal than in air, why?

10. Can two persons on hear the sound of each other? Explain.

**Long**

1. Discuss the effect of pressure, temperature and density of elastic medium on the velocity of sound.

2. What is Newton`s formula for the velocity of sound? What correction was made by Laplace?

3. Describe Newton`s expression for the velocity of sound in a gas.

4. Derive an expression for the velocity of sound in a medium by dimensional method. Discuss the effect of change in pressure and temperature on the velocity of sound in air.

5. Discuss Laplace`s correction and derive the formula for the velocity of sound in a gas.

6. State Newton`s formula for the velocity sound in gases. What correction was done by Laplace on it?

7. Explain the significance of Laplace`s correction of Newton`s formula for the velocity of sound derive the corrected formula.

8. Write down the factors on which the velocity of sound in air depends with necessary explanation.

9. Discuss Newton`s formula for the velocity of sound in a gas with Laplace`s correction.

10. Discuss Newton`s formula for the velocity of sound in air with Laplace`s correction.

11. Write an expression for the speed of sound in an ideal gas. Discuss the effect of change in temperature on the speed of sound.