7. What is the difference between longitudinal and transverse waves?

In longitudinal waves, the individual medium particles move in a direction parallel to the direction of propagation of the wave. In transverse waves, the individual particles of the medium move about their mean positions in a direction perpendicular to the direction of wave propagation.

8. An echo is heard 3 seconds after shouting near a mountain. Calculate the distance between the person and the mountain if the speed of sound is 340 m/s.

We know that the time taken for sound to travel to the mountain and back is twice the time taken to hear the echo.

So, time taken for sound to reach mountain = (3/2) seconds

Distance = Speed × time

Substituting the given values, we get:

Distance = 340 m/s × (3/2) s

Distance = 510 m

12. A person hears a sound of 2000 Hz. What is the wavelength of this sound if the speed of sound is 340 m/s?

We know that wavelength = velocity of sound / frequency

Substituting the given values, we get:

Wavelength = 340 m/s / 2000 Hz

Wavelength = 0.17 m

14. How does the frequency of a wave affect its pitch?

If the frequency of a wave increases, its pitch correspondingly increases. A sound of a higher pitch is called a shrill sound (e.g., the buzzing sound of a bee) but,  a sound of lower pitch is called a hoarse sound.

15. What is amplitude?

The magnitude of the maximum disturbance (in density or pressure) in the medium on either side of the mean value is called the amplitude of the wave (A). It depends on the magnitude of force with which the object is made to oscillate.

16. What is loudness?

Loudness of a sound is the perception made by the listener’s ear whether the given sound is a loud sound or a soft sound. The loudness or softness of a sound is basically dependent on its amplitude. Loudness is usually expressed in ‘decibels’ (dB).

17. What is the difference between loudness and intensity of sound?

Loudness is a measure of the response of the ear to the sound intensity. The amount of sound energy passing out through unit area in unit time around a point is called the intensity of sound at that point. The SI unit of intensity of sound is watt/m2 (W m-2)

22. What are the two laws of reflection that sound follows?

Sound follows the laws of reflection which state that (i) the incident sound wave, the reflected sound wave, and the normal to the reflecting surface are in the same plane, and (ii) the angle of incidence and angle of reflection are equal.

24. What is SONAR, and how is it used?

SONAR stands for Sound Navigation and Ranging, and it is a device that uses ultrasonic waves to measure the distance, direction, and speed of underwater objects. It is used to determine the depth of the sea and locate underwater hills, valleys, submarines, icebergs, and sunken ships.

25. How do we hear sounds?

Our ear converts pressure variations in air into electrical signals that travel via the auditory nerve to the brain. The ear has 3 parts: outer ear (collects sound), middle ear (amplifies sound vibrations), and inner ear (converts pressure variations to electrical signals).