Question

St.Mary'Convent matric hr sec school

Annual test-2021

Class: VIII SCIENCE Marks:25

I.CHOOSE THE CORRECT ANSWER: 6×1=6

1. The range of audible frequency for the human ear is

a) 2 Hz to 2000 Hz b) 20 Hz to 2000 Hz c) 20 Hz to 20000 Hz d) 200 Hz to 20000 Hz

2. Sound waves travel very fast in

a) air b) metals c) vacuum d) liquids

3. Find the odd one out.

a) Harmonium b) Flute c) Nadaswaram d) Violin

4. The amplitude of the sound wave decides its

a) speed b) pitch c) loudness d) frequency

5. Which of the following may be caused by noise?

a) Irratition b) Stress c) Nervousness d) All the above

6. Noise is produced by

a) vibrations with high frequency. b) regular vibrations.

c) regular and periodic vibrations. d) irregular and non-periodic vibrations.

II. FILL IN THE BLANKS : 4×1=4

7. Sound travels in the form of _________

8. Sound is produced by __________

9. If the thickness of a vibrating string is increased, its pitch ___________

10. The vibrations of a simple pendulum are also known as __________.

III. ANSWER THE FOLLOWING QUESTIONS (Any 5): 5×2=10

11.What is an ultrasonic sound?

12. What is vibration?

13. Define the following terms.(a). Amplitude (b). Loudness​

Answer 1

Answer:

1)20Hz to 20000Hz

2)solids

3)Violin

4)loudness

5) All the above

6)irregular and non-periodic vibrations.

1)waves

2)vibrates, creating a pressure wave.

3)Frequency

4) oscillation

1)Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" sound in its physical properties, except that humans cannot hear it. This limit varies from person to person and is approximately 20 kilohertz in healthy young adults

2)Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin vibrationem. The oscillations may be periodic, such as the motion of a pendulum—or random, such as the movement of a tire on a gravel road

3)Amplitude : It is defined as the maximum displacement produced in the vibrating particle on either side of the mean position. It is denoted by A. Its SI unit is metre.

Wavelength : It is defined as the distance travelled by a wave during the time a particle of the medium completes one vibration. It is denoted by k. Its SI unit is metre.

Frequency: It is the number of occurrences of a repeating event per unit of time. Its SI unit is Hertz (Hz).