SSC CGL Science – Waves & Sound – Tier II Level · Marathon

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SSC CGL Science – Waves & Sound – Tier II Level · Marathon – 11 questions, subject: General Science. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

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1.  
Two tuning forks of 512 Hz and 506 Hz are sounded together. The number of beats per second is:

Correct Answer: C [6]

Explanation:

Answer: 6. 512 − 506 = 6.

2.  
The fundamental frequency of a closed pipe 0.85 m long (v = 340 m/s) is:

Correct Answer: B [100 Hz]

Explanation:

Answer: 100 Hz. f = v/4L = 340/3.4 = 100 Hz.

3.  
For the same pipe opened at both ends, the fundamental frequency becomes:

Correct Answer: B [200 Hz]

Explanation:

Answer: 200 Hz. v/2L = 340/1.7 = 200 Hz.

4.  
A closed pipe has a fundamental of 120 Hz. Which of these can NOT be one of its overtones?

Correct Answer: A [240 Hz]

Explanation:

Only odd multiples: 360, 600, 840 … (3, 5, 7 × 120).

5.  
If the absolute temperature of air is made four times, the speed of sound becomes:

Correct Answer: C [two times]

Explanation:

Answer: two times. v ∝ √T.

6.  
A string 1 m long vibrates in its fundamental mode at 200 Hz. The speed of the wave on the string is:

Correct Answer: D [400 m/s]

Explanation:

Answer: 400 m/s. f = v/2L → v = 2 × 1 × 200.

7.  
A source of 680 Hz moves towards a stationary listener at 1/10 of the speed of sound. The frequency heard is about:

Correct Answer: C [756 Hz]

Explanation:

f' = f × v/(v − 0.1v) = 680/0.9 ≈ 755.6 Hz.

8.  
The sound level rises from 40 dB to 70 dB. The intensity becomes:

Correct Answer: B [1000 times]

Explanation:

Answer: 1000 times. 30 dB → 10³.

9.  
The speed of a wave on a stretched string is 100 m/s. If the tension is made four times, the speed becomes:

Correct Answer: A [200 m/s]

Explanation:

Answer: 200 m/s. v = √(T/μ) ∝ √T.

10.  
Assertion–ReasonAssertion (A): A closed organ pipe produces only odd harmonics.
Reason (R): Its closed end must be a node and its open end an antinode.

Correct Answer: D [Both A and R are true and R explains A]

Explanation:

Only odd quarter-wavelengths fit: L = (2n − 1) λ/4.

11.  
Data tableA signal generator drives a loudspeaker in a room – frequency (Hz): 170, 340, 680; measured wavelength (m): 2.0, 1.0, 0.5. The speed of sound in the room is:

Correct Answer: B [340 m/s]

Explanation:

v = f λ = 340 × 1 = 340 m/s for every row.

➤ Full notes, shortcuts and every answer explained – SSC CGL 2026 General Science book (₹149): www.shanmugamiasacademy.in/study-materials/ssc-cgl-general-science

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