Class 10 Physics Unit-11: Sound, Solved MCQs With Verified Answers. (National Book Foundation 2022 as Federal Text Book, Islamabad)

1. Which is NOT true for sound?

(a) Sound is produced by vibrating body
(b) Sound travels due to variations of pressure in the air
(c) Sound transfers energy along with the matter of medium
(d) Sound is a compressional and longitudinal wave

... Answer is (c) Sound transfers energy along with the matter of medium
Sound waves transfer energy but they do not transfer matter

2. Sound travels faster in ________

(a) Rubber
(b) Air
(c) Water
(d) Steel

... Answer is (d) Steel
Sound waves travel faster through solids as compared to liquids and gasses because in solids intermolecular distance is very small and the density of solids is greater than liquids and gases.

3. Speed of sound in air at 0°C is 332 m/s. What is its speed in a vacuum?

(a) Equal to 332 m/s
(b) Great than 332 m/s
(c) Less than 332 m/s
(d) Zero

... Answer is (d) Zero
Sound waves are mechanical waves that require a medium for their propagation. In a vacuum sound, waves do not travels.

4. Threshold of hearing has ________ intensity level.

(a) 0 dB
(b) 10 dB
(c) 120 dB
(d) 1 dB

... Answer is (a) 0 dB
The threshold of hearing is the sound level below which a person's ear is unable to detect any sound. (0 dB )

5. Frequency of sound waves in air is doubled, its speed will:

(a) Become half
(b) Become double
(c) Become four times
(d) Remain same

... Answer is (d) Remain same
v = f λ So doubling the frequency must halve the wavelength but the wave speed remains the same.

6. Sounds having frequency are called infrasonic waves:

(a) Greater than 20Hz
(b) Less than 20Hz
(c) 20 Hz
(d) 20 kHz

... Answer is (b) Less than 20Hz
The frequency range of below 20Hz is called infrasonic waves. Humans cannot detect it.

7. Minimum distance of a person from an obstacle for sound to hear an echo is: :

(a) 17 m
(b) 34 m
(c) 0.1 m
(d) any distance above 50 m

... Answer is (a) 17 m
d = 1/20th x value of sound waves

8. Which of the following properties of waves is directly related to the loudness of sound?

(a) Frequency
(b) Wavelength
(c) Speed
(d) Amplitude

... Answer is (d) Amplitude
Loudness of sound wave = ( Amplitude )²

9. . Intensity of threshold of pain (loudest audible sound without pain to ears):

(a) 10⁻¹² Wm⁻²
(b) 10 Wm⁻²
(c) 10¹² Wm⁻²
(d) 1 Wm⁻²

... Answer is (b) 10 Wm⁻²
Threshold of Pain = 10 Wm⁻² = 130 dB
 

10. Silent whistle is used to train dogs. When trainers blows the whistle, human beings do not hear it but dogs do listen. Its possible frequency is:

(a) f  > 20 Hz
(b) f ＜ 20 Hz
(c) f ＜ 20000 Hz
(d) f  > 20000 Hz

... Answer is (d) f > 20000 Hz
The most common Silent Whistles can emit a sound of a frequency of about 35 000 Hz that is greater than 20000 Hz. Dog hearing range is 67 Hz - 45,000 Hz.

************************************

Shortcut Links For 

1. National MDCAT, ECAT, JOB EXAM Physics Preparation (New) 
2. Physics 9th class main content List
3. Physics 9th class MCQs Quizzes All Units
4. Physics 10th class main content List
5. Physics 10th class MCQs Quizzes All Units

1. Website for School and College Level Physics   

(https://askrarequiz.blogspot.com)

2. Website for School and College Level Mathematics  

(https://askraremaths.blogspot.com)

3. Website for Single National Curriculum Pakistan - All Subjects Notes 

(https://askrareclassnotes.blogspot.com/)

© 2020-21 Academic Skills and Knowledge (ASK)     

Note:  Write to me in the comments box below for any query and also Share this information with your class-fellows and friends.