Waves

(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 → Compression (region of high pressure/density)
• R → 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:

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 → Incorrect
• It also says frequency increases during resonance → Incorrect

Correct concept: Step 3: Conclusion}

• Statement → Correct
• Reason → Incorrect

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):