Given below are the Class 9 Science Important Questions and worksheet for Sound
(a) Very shorts Answer based
(b) Match thec column
(c) Fill in the blanks
(d) Crossword Puzzle
(e)Short answer type
(f) Long answer type
Very Short Answer Based questions
Question 1
Arrange the speed of sound in Steel, water and air in ascending order?
What is the relation between frequency and time period of the wave?
Sound waves are transverse waves True or False?
Arrange the speed of these waves in air in descending order a) light b) Sound c) Supersonic aircraft?
What is an echo?
What are three characteristics of the sound
What is the audible range of sound frequencies for human ear?
What is Reflection of sound?
Answer
(i) air -> water -> steel
(ii) F=1/T
(iii) False
(iv) light -> Supersonic -> Sound
(v)The sound waves produced bounce back or gets reflected from the mountain or buildings and come to our ears, this reflected sound is known as Echo. To hear echo, the barrier reflecting the sound should be least at a distance of 17 meters
(vi) Amplitude,frequency/pitch and wavelength
(vii) 20Hz to 20KHz
(viii) Sound reflect like light only.The angle of incident is equal to the angle of reflection
Match the column
Question 2
Answer
Fill in the blanks
Question 3
(i)Sound waves …… travel in vacuum
(ii)The speed of sound depends on …………. And …………
(iii)The soft and porous materials are bad ………. Of sound
(iv)The speed of the highly penetrating ultrasonic waves are ………………….. those of audible sound waves
(v) The ……….. sound are produced before the main shock wave of earth quake
Answer
Do not
Nature of the material ,temperature
Reflectors
Same
infrasonic
Crossword Puzzle
Question 4 Across
4. It is used break kidney stones into fine grains
7. The unit of frequency
8. The loudness of the sound depends on this
9. Medical instrument used by the doctors for listening to heartbeats
10. It is the region of low pressure in longitudinal wave
Down
1. Apparatus used to find the depth of the sea
2. It converts sound wave frequency into electrical impulses
3. A vibrating simple pendulum produces this type of sound
5. It is the sensation of a frequency
6. Elevation in a transverse wave
Answer
Across
Ultrasound,Hertz, Amplitude, Stethoscope, rarefaction Down
Sonar, Cochlea, infrasonic, Pitch, crest
Short Answer type
Question 5
Why Sometimes we hear echo of sound.
Answer
We sometimes hear the echo of a sound produced because the distance between the source of the sound and the obstacle is at least 17.2
Question 6
What is a wave number?
Answer
The number of wavelengths present per unit length is called wave number. i.e. it is the reciprocal of wavelength = 1/λ.
Question 7
Are Sound waves mechanical waves?
Answer
Sound waves are mechanical waves as they need material medium for propagation which is the characteristic of the mechanical waves.
Question 8
A vibrating body produces sound. However, no sound is heard when a simple pendulum oscillates in air why?
Answer
Sound is produced only when the frequency of the wave is greater than 20 Hz. As a simple pendulum produces waves less than 20Hz they cannot be heard.
Question 9.
Define echo. Give its two application? Question 10.
Guess which sound has a higher pitch; guitar or car horn? Question 11
What type of waves can travel in vacuum? Give example(s).
Answer
Electromagnetic waves can travel in vacuum. Sun light, X-rays are examples of electromagnetic waves.
Question 12
Why Ceiling of good conference halls and concert halls are curved?
Answer
Ceiling of good conference halls and concert halls are curved so that the sound waves after reflecting from these walls reaches every part of the hall and can be easily heard by the listeners.
Long Answer type
Question 13.
Write full form of acronym SONAR. How the method of echo-ranging is used to detetmine the depth of the sea? Question 14.
Explain, how defects in a metal block can be detected using ultrasound? Question 15.
Why do we hear more clearly in a room with curtains than in a room without curtains? Explain in brief? Question 16.
Explain giving reason the purpose of using curved ceilings in cinema halls? Question 17
(i) Define the time period of a wave.
(ii) Give the relation among speed of sound v, wavelength λ and its frequency f.
Answer
(i) Time period (T)
It is defined as the time required to complete one wave.
(ii) Speed of sound (v) = Wavelength ( λ ) × Frequency ( f )
Question 18.
Draw a graph showing density and pressure variations with respect to distance for a disturbance produced by sound wave? Mark the position of compression and rarefaction on this curve/graph. Name the regions of maximum and minimum change in pressure respectively? Question 19.
Explain with the help of bell jar experiment that sound cannot travel in vaccum? Question 20.
(a) Define wavelength?
(b) Which characteristic of the sound helps you to identify your friend by his voice while sitting with others in a darkroom?
(c) Which wave property determines pitch? Question 21.
What is a transverse wave? Question 22.
Why do we hear the sound produced by a humming bees while sound of vibrations of a simple pendulum is not heard?
Summary
This Class 9 Science Important Questions and worksheet for Sound is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail.
