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Secondary 4 Pure Physics Waves Sound Light Quiz
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Questions
Secondary 4 Pure Physics Quiz - Waves Sound Light
Name: _________________________ Class: _________________________ Date: _________________________ Score: ______ / 40
Duration: 45 minutes Total Marks: 40
Instructions:
- Answer ALL questions in the spaces provided.
- Show all working for calculation questions.
- Take g = 10 m/s² unless otherwise stated.
- The number of marks is given in brackets [ ] at the end of each question or part question.
Section A: Wave Properties (Questions 1–5)
Total: 10 marks
1. State two differences between transverse waves and longitudinal waves. [2]
2. A wave has a frequency of 250 Hz and a wavelength of 1.4 m.
(a) Calculate the speed of this wave. [2]
(b) Calculate the period of this wave. [1]
3. Figure 3.1 shows a displacement-distance graph for a wave at a particular instant.
Displacement (cm)
^
2 | /\
| / \
0 |--/----\------------------> Distance (m)
| \ /
-2 | \/
+--+--+--+--+--+--+--+--
2 4 6 8 10 12
(a) Determine the amplitude of this wave. [1]
(b) Determine the wavelength of this wave. [1]
4. Explain why sound cannot travel through a vacuum. [2]
5. A student makes the following statement: "Waves transfer matter from one place to another."
State whether this statement is correct and explain your answer. [1]
Section B: Sound (Questions 6–10)
Total: 10 marks
6. A loudspeaker produces a sound wave of frequency 440 Hz.
(a) State what is meant by the frequency of a sound wave. [1]
(b) The speed of sound in air is 340 m/s. Calculate the wavelength of this sound wave. [2]
7. A musician plays a note on a guitar and then plays a louder note of the same pitch.
Describe how the sound wave changes in terms of: (a) amplitude [1]
(b) frequency [1]
8. An echo is heard 0.8 s after a sound is made. The speed of sound in air is 340 m/s.
Calculate the distance between the source and the reflecting surface. [2]
9. Ultrasound is used in medical imaging to examine a developing foetus.
(a) State the typical frequency range for ultrasound. [1]
(b) Explain one advantage of using ultrasound rather than X-rays for this purpose. [1]
10. A ship uses sonar to detect a shoal of fish. A pulse of sound is emitted and the reflected pulse is received 0.15 s later. The speed of sound in water is 1500 m/s.
Calculate the distance of the shoal from the ship. [1]
Section C: Light – Reflection and Refraction (Questions 11–15)
Total: 10 marks
11. State the law of reflection. [1]
12. A ray of light travels from air into glass. The angle of incidence is 45° and the angle of refraction is 28°.
Calculate the refractive index of the glass. [2]
13. Figure 13.1 shows a ray of light travelling from water into air.
Air
----------------
\ |
\ |
\| Water
\
\
(a) State what is meant by the critical angle. [1]
(b) Explain what happens to the ray of light when the angle of incidence in the water is greater than the critical angle. [2]
14. Optical fibres use total internal reflection to transmit light signals.
(a) State one condition necessary for total internal reflection to occur. [1]
(b) State one application of optical fibres in communications. [1]
15. The speed of light in a vacuum is 3.0 × 10⁸ m/s. The speed of light in a certain type of glass is 2.0 × 10⁸ m/s.
Calculate the refractive index of this glass. [2]
Section D: Lenses and Electromagnetic Spectrum (Questions 16–20)
Total: 10 marks
16. A converging lens has a focal length of 10 cm. An object is placed 25 cm from the lens.
(a) State what type of image is formed (real or virtual). [1]
(b) State whether the image is magnified or diminished. [1]
17. Draw a labelled ray diagram to show how a converging lens forms an image when the object is placed beyond 2F (twice the focal length). [3]
Use the space below for your diagram. Label the object, image, lens, F, and 2F.
18. State the seven regions of the electromagnetic spectrum in order of increasing frequency. [2]
19. State one application for each of the following types of electromagnetic radiation:
(a) Infrared [1]
(b) Ultraviolet [1]
20. All electromagnetic waves travel at the same speed in a vacuum.
State this speed and explain why different types of electromagnetic waves have different properties despite travelling at the same speed. [1]
END OF QUIZ
Answers
Secondary 4 Pure Physics Quiz - Waves Sound Light
ANSWER KEY AND MARKING SCHEME
Total Marks: 40
Section A: Wave Properties (Questions 1–5)
1. State two differences between transverse waves and longitudinal waves. [2]
| Mark | Answer |
|---|---|
| [1] | In transverse waves, particles oscillate perpendicular to the direction of wave travel / energy transfer. In longitudinal waves, particles oscillate parallel to the direction of wave travel / energy transfer. |
| [1] | Transverse waves have crests and troughs; longitudinal waves have compressions and rarefactions. |
Accept any two valid differences. Award [1] for each correct difference stated clearly.
2. (a) Calculate the speed of this wave. [2]
| Mark | Working |
|---|---|
| [1] | v = fλ |
| [1] | v = 250 × 1.4 = 350 m/s |
Answer: 350 m/s. Award [1] for correct formula, [1] for correct answer with units.
(b) Calculate the period of this wave. [1]
| Mark | Working |
|---|---|
| [1] | T = 1/f = 1/250 = 0.004 s or 4.0 × 10⁻³ s |
Answer: 0.004 s or 4.0 ms. Accept 4 × 10⁻³ s.
3. (a) Determine the amplitude of this wave. [1]
| Mark | Answer |
|---|---|
| [1] | 2 cm or 0.02 m |
(b) Determine the wavelength of this wave. [1]
| Mark | Answer |
|---|---|
| [1] | 8 m (distance between two consecutive crests or troughs) |
4. Explain why sound cannot travel through a vacuum. [2]
| Mark | Answer |
|---|---|
| [1] | Sound is a longitudinal wave that requires a medium to travel through. |
| [1] | Sound travels by particles vibrating and passing on energy through collisions. In a vacuum, there are no particles to vibrate, so sound cannot propagate. |
Award [1] for stating sound needs a medium, [1] for explaining that a vacuum has no particles/matter to transmit vibrations.
5. State whether this statement is correct and explain your answer. [1]
| Mark | Answer |
|---|---|
| [1] | The statement is incorrect. Waves transfer energy from one place to another without transferring matter. Particles in the medium oscillate about fixed positions but do not travel with the wave. |
Section B: Sound (Questions 6–10)
6. (a) State what is meant by the frequency of a sound wave. [1]
| Mark | Answer |
|---|---|
| [1] | Frequency is the number of complete oscillations / cycles / waves per second. OR Frequency is the number of waves passing a point per unit time. Measured in hertz (Hz). |
(b) Calculate the wavelength of this sound wave. [2]
| Mark | Working |
|---|---|
| [1] | λ = v/f |
| [1] | λ = 340/440 = 0.773 m (accept 0.77 m or 0.773 m) |
Answer: 0.77 m (to 2 significant figures). Award [1] for correct formula, [1] for correct answer with units.
7. (a) Describe how the sound wave changes in terms of amplitude. [1]
| Mark | Answer |
|---|---|
| [1] | The amplitude increases (because the sound is louder). |
(b) Describe how the sound wave changes in terms of frequency. [1]
| Mark | Answer |
|---|---|
| [1] | The frequency remains the same (because the pitch is unchanged). |
8. Calculate the distance between the source and the reflecting surface. [2]
| Mark | Working |
|---|---|
| [1] | Total distance travelled by sound = v × t = 340 × 0.8 = 272 m |
| [1] | Distance to reflecting surface = total distance ÷ 2 = 272 ÷ 2 = 136 m |
Answer: 136 m. Award [1] for calculating total distance, [1] for halving to find one-way distance.
9. (a) State the typical frequency range for ultrasound. [1]
| Mark | Answer |
|---|---|
| [1] | Above 20,000 Hz / above 20 kHz (beyond the range of human hearing). |
(b) Explain one advantage of using ultrasound rather than X-rays for this purpose. [1]
| Mark | Answer |
|---|---|
| [1] | Ultrasound does not use ionising radiation, so it is safer for the developing foetus. OR Ultrasound can produce real-time images of soft tissue without harmful effects. |
Accept any valid advantage related to safety or imaging capability.
10. Calculate the distance of the shoal from the ship. [1]
| Mark | Working |
|---|---|
| [1] | Distance = (v × t) ÷ 2 = (1500 × 0.15) ÷ 2 = 225 ÷ 2 = 112.5 m |
Answer: 112.5 m or 113 m. Award [1] for correct answer with units.
Section C: Light – Reflection and Refraction (Questions 11–15)
11. State the law of reflection. [1]
| Mark | Answer |
|---|---|
| [1] | The angle of incidence equals the angle of reflection. OR The incident ray, reflected ray, and normal all lie in the same plane, and the angle of incidence equals the angle of reflection. |
12. Calculate the refractive index of the glass. [2]
| Mark | Working |
|---|---|
| [1] | n = sin i / sin r |
| [1] | n = sin 45° / sin 28° = 0.7071 / 0.4695 = 1.51 (accept 1.5) |
Answer: 1.5 (to 2 significant figures). Award [1] for correct formula, [1] for correct substitution and answer.
13. (a) State what is meant by the critical angle. [1]
| Mark | Answer |
|---|---|
| [1] | The critical angle is the angle of incidence in the denser medium for which the angle of refraction in the less dense medium is 90°. |
(b) Explain what happens when the angle of incidence is greater than the critical angle. [2]
| Mark | Answer |
|---|---|
| [1] | Total internal reflection occurs. |
| [1] | All the light is reflected back into the denser medium (water); no light is refracted into the air. |
Award [1] for stating total internal reflection, [1] for explaining that all light is reflected.
14. (a) State one condition necessary for total internal reflection to occur. [1]
| Mark | Answer |
|---|---|
| [1] | Light must travel from a denser medium to a less dense medium. OR The angle of incidence in the denser medium must be greater than the critical angle. |
(b) State one application of optical fibres in communications. [1]
| Mark | Answer |
|---|---|
| [1] | Transmission of telephone/internet signals / cable television / high-speed data transmission. |
Accept any valid application.
15. Calculate the refractive index of this glass. [2]
| Mark | Working |
|---|---|
| [1] | n = speed of light in vacuum / speed of light in medium |
| [1] | n = (3.0 × 10⁸) / (2.0 × 10⁸) = 1.5 |
Answer: 1.5. Award [1] for correct formula, [1] for correct answer.
Section D: Lenses and Electromagnetic Spectrum (Questions 16–20)
16. (a) State what type of image is formed (real or virtual). [1]
| Mark | Answer |
|---|---|
| [1] | Real (object is beyond F, so a real image is formed on the opposite side of the lens). |
(b) State whether the image is magnified or diminished. [1]
| Mark | Answer |
|---|---|
| [1] | Diminished (object is beyond 2F, so the image is smaller than the object). |
17. Draw a labelled ray diagram. [3]
| Mark | Criteria |
|---|---|
| [1] | Correct lens symbol and principal axis drawn with F and 2F labelled on both sides. |
| [1] | At least two correct rays drawn from the top of the object: (i) ray parallel to principal axis, refracted through F on the other side; (ii) ray through the optical centre, undeviated. |
| [1] | Image correctly located between F and 2F on the opposite side, labelled as real, inverted, and diminished. |
Diagram should show: object beyond 2F on left side; image between F and 2F on right side; image is inverted, real, and diminished.
18. State the seven regions of the electromagnetic spectrum in order of increasing frequency. [2]
| Mark | Answer |
|---|---|
| [1] | Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays (correct order). |
| [1] | All seven regions named correctly. |
Award [1] for correct order, [1] for all seven regions. Deduct [1] if order is incorrect. Accept increasing frequency or decreasing wavelength.
19. State one application for each:
(a) Infrared [1]
| Mark | Answer |
|---|---|
| [1] | Remote controls / thermal imaging / infrared heaters / night vision cameras / optical fibre communication. |
(b) Ultraviolet [1]
| Mark | Answer |
|---|---|
| [1] | Sterilisation of medical equipment / detecting forged banknotes / sunbeds / fluorescent lamps / water purification. |
20. State this speed and explain why different types of electromagnetic waves have different properties. [1]
| Mark | Answer |
|---|---|
| [1] | Speed in vacuum = 3.0 × 10⁸ m/s. Different types of EM waves have different frequencies and wavelengths. Although they travel at the same speed in a vacuum, their different frequencies/wavelengths give them different energies and different interactions with matter. |
Award [1] for stating the speed and explaining that different frequencies/wavelengths cause different properties.
END OF ANSWER KEY