[(c)] If the distance between two consecutive āCā of the wave is , which is travelling with a speed of , will it be audible to humans? Justify your answer by mathematical calculation.
Official Solution
Correct Option: (1)
(a) Type of wave Concept:
The diagram shows regions of compression (C) and rarefaction (R), which are characteristics of longitudinal waves. Answer:(b) Meaning of C and R
C ā Compression (region of high pressure/density)
R ā Rarefaction (region of low pressure/density)
(c) Audibility of the wave Step 1: Given data} Step 2: Formula} Step 3: Calculation} Step 4: Compare with human hearing range}
Human audible range:
Step 5: Conclusion}
So, the sound is:
02
PYQ 2026
medium
physicsID: kerala-s
Statement: If the stem of a tuning fork is placed on a table, the sound heard increases.
Reason: If the frequency of the forcing object and the natural frequency of the forced object are not equal, then objects are said to be in resonance. The frequency of the object undergoing resonance will increase.
1
Both the Statement and Reason are correct.
2
Both the Statement and Reason are incorrect.
3
The Statement is correct but the Reason is incorrect.
4
The Statement is wrong but the Reason is correct.
Official Solution
Correct Option: (3)
Concept: Resonance and Sound Amplification Step 1: Analyze the Statement}
When the stem of a tuning fork is placed on a table:
The table acts as a sounding board.
It increases the surface area vibrating.
This amplifies the sound produced.
Hence, the Statement is correct. Step 2: Analyze the Reason}
The Reason states:
Resonance occurs when frequencies are not equal ā Incorrect
It also says frequency increases during resonance ā Incorrect
Correct concept:
Step 3: Conclusion}
Statement ā Correct
Reason ā Incorrect
03
PYQ 2026
medium
physicsID: kerala-s
A child standing between two large buildings claps and hears the echo from the first building in 0.2 seconds and the echo from the second building in 0.3 seconds. (Speed of sound in air = )
[(a)] What is the condition to produce an echo?
[(b)] Calculate the distance between the two buildings.
Official Solution
Correct Option: (1)
Concept: Echo and Sound Reflection
An echo is produced due to reflection of sound waves from a distant surface. Part (a): Condition to produce an echo Step 1: Time condition}
For a distinct echo to be heard, the reflected sound must reach the ear after at least:
Step 2: Minimum distance condition}
Using speed of sound:
Conclusion (a):Part (b): Distance between two buildings Step 1: Distance to first building}
Echo time = s (round trip)
Step 2: Distance to second building}
Echo time = s
Step 3: Total distance between buildings} Conclusion (b):
