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🌊 WAVES (Mechanical Waves)

Objective Questions – Page 6 (Advanced Level)

Q51️⃣ (Numerical – Tough)

A wave on a string is represented by
y = 0.01 sin(5x − 200t) (SI units).
The wave speed is:

A) 20 m/s
B) 40 m/s
C) 50 m/s
D) 80 m/s

Answer: B

Logic: v = ω / k = 200 / 5 = 40 m/s

Q52️⃣ (Multi-Correct)

Which statements about mechanical waves are correct?

A) Particles move in direction of wave propagation
B) Energy is transferred through medium
C) Medium particles execute oscillatory motion
D) Waves can travel in vacuum

Correct Options: B, C

Q53️⃣ (Conceptual – Boundary Conditions)

At a rigid boundary, reflection of a wave causes:

A) Phase reversal
B) No phase change
C) Node formation
D) Antinode formation

Correct Options: A, C

Q54️⃣ (Numerical – Standing Waves)

A string fixed at both ends has length 1.5 m. If fundamental frequency is 100 Hz, wave speed is:

A) 150 m/s
B) 200 m/s
C) 300 m/s
D) 400 m/s

Answer: C

Formula: v = 2Lf

Q55️⃣ (Assertion–Reason)

Assertion (A): Speed of sound increases with temperature.
Reason (R): Kinetic energy of molecules increases with temperature.

A) A & R true, R explains A
B) A & R true, R does not explain A
C) A true, R false
D) A false, R true

Answer: A

Q56️⃣ (Numerical – Beats)

Two tuning forks produce 4 beats per second. If frequency of one fork is 256 Hz, possible frequency of other fork is:

A) 252 Hz
B) 260 Hz
C) 254 Hz
D) 260 Hz only

Correct Options: A, B

Q57️⃣ (Conceptual – Doppler Effect)

If both source and observer move towards each other, the observed frequency:

A) Increases
B) Decreases
C) Remains same
D) Becomes zero

Answer: A

Q58️⃣ (Numerical – Organ Pipe)

A closed organ pipe has fundamental frequency 200 Hz. Its first overtone frequency is:

A) 200 Hz
B) 300 Hz
C) 400 Hz
D) 600 Hz

Answer: D

Q59️⃣ (Tricky)

Which quantity remains unchanged when a wave enters another medium?

A) Speed
B) Wavelength
C) Frequency
D) Amplitude