NUMS — Medical & Dental Entry Test

NUMS Physics — Waves, Sound, Optics and Thermodynamics (Set 2)

Take the NUMS Physics — Waves, Sound, Optics and Thermodynamics (Set 2): 30 multiple-choice questions (40 minutes) with instant scoring and a full answer…

What this test covers

30 NUMS Physics

Sample questions with answers

The first 5 questions of this test, with the correct answer and explanation.

Q1. The displacement of a vibrating particle is x = 0.05 sin(10t) metres, with t in seconds. What is its maximum speed?
- A. 50 m s⁻¹
- B. 0.5 m s⁻¹ ✓
- C. 5 m s⁻¹
- D. 0.05 m s⁻¹
Answer: B. 0.5 m s⁻¹
Explanation: For x = A sin ωt, v_max = Aω = 0.05 × 10 = 0.5 m s⁻¹.
Q2. A particle in SHM has displacement x = 0.02 sin(10πt) metres. What is the frequency of oscillation?
- A. 31.4 Hz
- B. 5 Hz ✓
- C. 10 Hz
- D. 0.2 Hz
Answer: B. 5 Hz
Explanation: ω = 10π rad s⁻¹ and f = ω/2π = 10π/2π = 5 Hz.
Q3. A pendulum clock that keeps correct time on Earth is taken to the Moon, where g is one-sixth of Earth's value. How does its period change?
- A. It becomes √6 times longer ✓
- B. It becomes 6 times longer
- C. It does not change
- D. It becomes √6 times shorter
Answer: A. It becomes √6 times longer
Explanation: T = 2π√(L/g); reducing g by a factor of 6 increases T by √6 ≈ 2.45, so the clock runs slow.
Q4. What length of simple pendulum has a period of 2.0 s where g = 9.8 m s⁻²?
- A. 0.50 m
- B. 1.98 m
- C. 3.92 m
- D. 0.99 m ✓
Answer: D. 0.99 m
Explanation: L = gT²/4π² = 9.8 × 4 / 39.5 ≈ 0.99 m (the 'seconds pendulum').
Q5. The shock absorbers of an ambulance are designed so that the springs stop oscillating quickly after a bump. This is an application of:
- A. forced oscillation at the natural frequency
- B. resonance, which increases the amplitude
- C. damping, which dissipates the oscillation energy ✓
- D. simple harmonic motion with constant amplitude
Answer: C. damping, which dissipates the oscillation energy
Explanation: Dampers convert the kinetic energy of the oscillation into heat (viscous friction), so the amplitude dies away rapidly.

The other 25 questions

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Q6. In simple harmonic motion, what is the phase difference between displacement and velocity?
- A. Zero
- B. 2π radians
- C. π/2 radians
- D. π radians
Q7. Sound waves in air cannot be polarised. What does this show about them?
- A. They do not carry energy
- B. They are transverse waves
- C. They are electromagnetic waves
- D. They are longitudinal waves
Q8. The tension in a stretched string is made four times larger while its mass per unit length is unchanged. What happens to the speed of transverse waves on it?
- A. It becomes four times larger
- B. It doubles
- C. It does not change
- D. It halves
Q9. In which medium does sound travel fastest?
- A. Water
- B. Air
- C. Steel
- D. Vacuum
Q10. A cyclist rides at 34 m s⁻¹ towards a stationary siren emitting 500 Hz. What frequency does the cyclist hear? (speed of sound = 340 m s⁻¹)
- A. 556 Hz
- B. 500 Hz
- C. 450 Hz
- D. 550 Hz
Q11. A string 1.0 m long is fixed at both ends, and waves travel along it at 200 m s⁻¹. What is the frequency of its third harmonic?
- A. 150 Hz
- B. 100 Hz
- C. 600 Hz
- D. 300 Hz
Q12. Fork A (256 Hz) produces 4 beats per second with fork B. When B is loaded with a little wax, the beat frequency increases. What was the frequency of B before loading?
- A. 256 Hz
- B. 248 Hz
- C. 260 Hz
- D. 252 Hz
Q13. Why does medical ultrasound imaging use frequencies of several megahertz rather than audible frequencies?
- A. High frequencies travel faster in tissue
- B. The short wavelength allows small structures to be resolved
- C. High frequencies are not reflected at boundaries
- D. Audible sound cannot enter the body
Q14. The intensity of sound in a busy hospital corridor is 1.0 × 10⁻⁶ W m⁻². What is the sound intensity level? (I₀ = 1.0 × 10⁻¹² W m⁻²)
- A. 6 dB
- B. 120 dB
- C. 40 dB
- D. 60 dB
Q15. Two coherent waves meet at a point. What path difference produces completely destructive interference?
- A. A whole number of wavelengths, nλ
- B. Zero path difference
- C. An odd number of half wavelengths, (n + ½)λ
- D. Exactly 2λ
Q16. In Young's double-slit experiment, the separation between the slits is doubled while everything else is unchanged. What happens to the fringe spacing?
- A. It becomes four times larger
- B. It doubles
- C. It is unchanged
- D. It halves
Q17. A diffraction grating has 600 lines per millimetre and is lit normally with light of wavelength 500 nm. What is the highest order of maximum that can be observed?
- A. 4
- B. 2
- C. 3
- D. 6
Q18. Unpolarised light of intensity I₀ passes through two polaroids whose transmission axes are at 60° to each other. What intensity emerges?
- A. I₀/4
- B. 3I₀/8
- C. I₀/8
- D. I₀/2
Q19. A swimming pool is 2.0 m deep. To a person looking vertically down, how deep does it appear? (refractive index of water = 4/3)
- A. 2.7 m
- B. 1.0 m
- C. 2.0 m
- D. 1.5 m
Q20. An object is placed 30 cm from a converging lens of focal length 20 cm. Where is the image formed and what is its nature?
- A. 60 cm behind the lens; real, inverted and twice the size
- B. 12 cm in front of the lens; virtual and erect
- C. 60 cm in front of the lens; virtual and magnified
- D. 12 cm behind the lens; real and diminished
Q21. A converging lens of power +2.0 D is placed in contact with a diverging lens of power −0.5 D. What is the focal length of the combination?
- A. 40 cm
- B. 150 cm
- C. 66.7 cm
- D. 25 cm
Q22. An elderly patient can see distant objects clearly but cannot read a book held at normal distance (long-sightedness). Which lens corrects this?
- A. A converging (convex) lens
- B. A cylindrical lens only
- C. A plane glass sheet
- D. A diverging (concave) lens
Q23. An astronomical telescope has an objective of focal length 100 cm and an eyepiece of focal length 5 cm, adjusted for normal viewing. What is its magnifying power?
- A. 20
- B. 95
- C. 105
- D. 500
Q24. In an optical fibre used in an endoscope, what must be true of the cladding around the core?
- A. It must have the same refractive index as the core
- B. Its refractive index must be lower than that of the core
- C. Its refractive index must be higher than that of the core
- D. It must be opaque
Q25. Air in a syringe is compressed at a constant pressure of 2.0 × 10⁵ Pa from 5.0 L to 3.0 L. How much work is involved?
- A. 400 J done by the gas
- B. 4.0 × 10⁵ J done on the gas
- C. 400 J done on the gas
- D. 40 J done on the gas
Q26. 500 J of heat is supplied to a gas in a sealed rigid container. What is the change in its internal energy?
- A. +500 J, since no work is done at constant volume
- B. Zero, since the volume does not change
- C. −500 J
- D. +250 J, as half the heat does work
Q27. What is the ratio γ = Cp/Cv for a monatomic ideal gas such as helium?
- A. 7/5
- B. 4/3
- C. 5/3
- D. 3/2
Q28. A Carnot engine rejects heat to a sink at 300 K and has an efficiency of 25%. What is the temperature of its source?
- A. 375 K
- B. 225 K
- C. 1200 K
- D. 400 K
Q29. 3000 J of heat flows reversibly into a large reservoir kept at 300 K. What is the change in entropy of the reservoir?
- A. −10 J K⁻¹
- B. +0.1 J K⁻¹
- C. +9 × 10⁵ J K⁻¹
- D. +10 J K⁻¹
Q30. A gas has density 1.2 kg m⁻³ at a pressure of 1.0 × 10⁵ Pa. Using P = ⅓ρ⟨v²⟩, what is the root-mean-square speed of its molecules?
- A. 250 000 m s⁻¹
- B. 500 m s⁻¹
- C. 289 m s⁻¹
- D. 158 m s⁻¹