Available Answers

1. 1.

   Fill in the blanks:

   1. SONAR stands for _____________.
   2. The minimum distance at which the reflecting surface should be present for occurrence of echo is _____________.
   3. Speed of sound is _____________ in liquids than gases.
   4. Two good reflectors of sound are _____________ and _____________.
   5. Two bad reflectors of sound are _____________ and _____________.
   6. Sound travels in all possible _____________.
2. 2.

   State whether the following statements are true (T) or false (F). Correct the false statements:

   1. Loudness of a sound depends on the frequency of the sound wave.
   2. The Sl unit of amplitude is metre.
   3. The region in air where particles are compressed together is known as rarefaction.
   4. The pitch of a sound differentiates a shrill sound from a flat sound.
3. 3.

   Fill in the blanks:

   1. Sound is a form of ____________.
   2. The speed of sound is ____________ in different media.
   3. Sound travels ____________ in solids than in gases.
   4. ____________a sound depends on the amplitude of the wave.
   5. Frequency measured in ____________.
   6. Our ear can hear two sounds distinctly if they reach us after a gap of ____________ second(s).
4. 4.

   State whether the following statements are true (T) or false (F). Correct the false statements:

   1. Only living things produce sound.
   2. Sound travels in all possible directions.
   3. Sound can propagate everywhere, even in vacuum.
   4. Sound is a longitudinal wave.
   5. Good reflectors of sound produce good echoes.
   6. When sound is reflected, angle of incidence is twice the angle of reflection.
5. 5.

   Choose the correct option:

   1. Sound can travel through ______________.
   2. Amplitude has the same units as that of ____________.
   3. The minimum distance for the occurrence of an echo is ______________.
   4. Flute is an example of _______________ instrument.
   5. The speed of sound in air is ______________.
   6. Of the following, which is a good reflector of sound?
6. 6.

   Match the columns:

   Column A	Column B
   Wavelength Frequency  Violin  Trumpet Drum	Wind instrument Angstrom Percussion instrument Stringed instrument Hertz