NUST NET Physics chapter 3: Physics · Oscillations, waves and light MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

42 exam-style questions on Physics · Oscillations, waves and light, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

42 questions · 3 topics · 10 per test

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What chapter 3 covers

Ten Physics · Oscillations, waves and light questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. The fact that light can be polarised shows that light

  1. A
    travels in straight lines
  2. B
    is a longitudinal wave
  3. C
    is made up of particles
  4. D
    is a transverse wave
Show answer

Answer: D. Only transverse waves have a direction of vibration at right angles to travel that a polariser can select. Longitudinal waves such as sound cannot be polarised.

2. Light of wavelength 500 nm falls normally on a diffraction grating. For a first-order maximum to be formed at all, the number of lines per centimetre must be less than

  1. A
    2.0 × 106
  2. B
    2.0 × 104
  3. C
    1.0 × 104
  4. D
    5.0 × 10−5
Show answer

Answer: B. d sin θ = λ needs sin θ = λ/d to be less than 1, so d must exceed λ = 5.0 × 10−5 cm. Lines per cm = 1/d, which must be less than 1/(5.0 × 10−5) = 2.0 × 104. 2.0 × 106 is the limit per metre, and 1.0 × 104 is the limit for a second-order maximum.

3. An astronomical telescope in normal adjustment is 44 cm long and has a magnifying power of 10. The focal lengths of its objective and eyepiece are

  1. A
    4 cm and 40 cm
  2. B
    40 cm and 4 cm
  3. C
    22 cm and 22 cm
  4. D
    44 cm and 4.4 cm
Show answer

Answer: B. In normal adjustment the length is fo + fe = 44 cm and M = fo/fe = 10. So fe = 4 cm and fo = 40 cm: the objective has the longer focal length.

4. A particle in SHM with period T starts from its mean position. The shortest time it takes to reach half its amplitude is

  1. A
    T/8
  2. B
    T/6
  3. C
    T/4
  4. D
    T/12
Show answer

Answer: D. x = x0 sin(2πt/T) = x0/2 when 2πt/T = π/6, so t = T/12. It is less than T/8 because the particle moves fastest near the mean position.

5. A train sounding its whistle passes a person standing beside the track. The pitch heard is 600 Hz as the train approaches and 400 Hz as it moves away. Taking the speed of sound as 340 m s−1, the speed of the train is

  1. A
    34 m s−1
  2. B
    85 m s−1
  3. C
    113 m s−1
  4. D
    68 m s−1
Show answer

Answer: D. 600/400 = (v + u)/(v − u) = 1.5, so u = v/5 = 68 m s−1. Writing u = v(600 − 400)/600 gives 113 m s−1.

6. A 0.10 kg mass on a spring oscillates with angular frequency 20 rad s−1 and amplitude 5.0 cm. Its total energy is

  1. A
    0.10 J
  2. B
    1.0 J
  3. C
    500 J
  4. D
    0.050 J
Show answer

Answer: D. E = ½mω2x02 = ½ × 0.10 × 400 × (0.050)2 = 0.050 J. Leaving out the ½ gives 0.10 J, and not squaring the amplitude gives 1.0 J.

7. Tuning forks of frequencies 510 Hz and 512 Hz are sounded together. The time between two successive loud sounds (maxima) is

  1. A
    0.50 s
  2. B
    2.0 s
  3. C
    0.25 s
  4. D
    2.0 ms
Show answer

Answer: A. Beat frequency = 512 − 510 = 2 Hz, so successive maxima are 1/2 = 0.50 s apart. 2.0 s confuses the beat frequency with the beat period.

8. The spectral lines in light from a distant galaxy are shifted towards longer wavelengths (a red shift). This shows that the galaxy

  1. A
    is moving away from the Earth
  2. B
    is moving towards the Earth
  3. C
    is hotter than the Sun
  4. D
    is at rest relative to the Earth
Show answer

Answer: A. By the Doppler effect a source moving away is received at a lower frequency, that is a longer wavelength. Approach would give a blue shift.

9. A pipe open at both ends resonates at 510 Hz and at 680 Hz, with no resonance between these frequencies. Its fundamental frequency is

  1. A
    85 Hz
  2. B
    340 Hz
  3. C
    170 Hz
  4. D
    1190 Hz
Show answer

Answer: C. An open pipe resonates at every whole-number multiple of its fundamental, so neighbouring resonances differ by f0: 680 − 510 = 170 Hz (510 = 3 × 170 and 680 = 4 × 170). Halving the difference (85 Hz) is the rule for a closed pipe, whose resonances go up in steps of 2f0.

10. In Young's double-slit experiment λ = 480 nm, the slit separation is 0.24 mm and the screen is 1.5 m away. How far from the centre of the pattern is the third bright fringe?

  1. A
    3.0 mm
  2. B
    7.5 mm
  3. C
    6.0 mm
  4. D
    9.0 mm
Show answer

Answer: D. ym = mλL/d = (3 × 4.8 × 10−7 × 1.5)/(2.4 × 10−4) = 9.0 × 10−3 m = 9.0 mm. 7.5 mm is the third dark fringe, and 3.0 mm is the fringe spacing.

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Ways to practise this chapter

Physics · Oscillations, waves and light: questions students ask

How many Physics · Oscillations, waves and light MCQs are there?

42, each with the answer and a short explanation, across 3 topics: Oscillations, Waves and sound, Physical optics and optical instruments. Every chapter test draws ten of them, so you can take it many times.

Is the NUST NET Physics chapter 3 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

Can I read the explanations in Urdu?

Yes. In practice mode and on your results you can switch the explanations to Urdu.

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