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O Level Physics Waves Sound Light Quiz

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Questions

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O-Level 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 clearly for calculation questions.
  • State units in all final answers.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • You may use a calculator.

Section A: General Wave Properties [10 marks]

1. A wave travels along a stretched rope. The diagram below shows the rope at a particular instant.

    Displacement / cm
        ^
    2.0 |    /\      /\
        |   /  \    /  \
    0.0 |--/----\--/----\---> Distance / cm
        | /      \/      \
   -2.0 |/                \
        +--|--|--|--|--|--|-->
          0  20 40 60 80 100

(a) State the amplitude of the wave. [1]

(b) Determine the wavelength of the wave. [1]

(c) The wave has a frequency of 5.0 Hz. Calculate the speed of the wave. [2]

2. A student investigates water waves in a ripple tank. The waves travel from deep water into shallow water.

(a) State what happens to the speed of the waves as they enter the shallow water. [1]

(b) The frequency of the waves remains constant. Explain why the wavelength changes when the waves enter the shallow water. [2]

3. Distinguish between transverse waves and longitudinal waves. Give one example of each. [3]

4. A wave in a ripple tank has a frequency of 12 Hz and a wavelength of 2.0 cm.

(a) Calculate the speed of the wave. [2]

(b) State two ways in which the speed of a water wave could be changed in a ripple tank. [2]

5. A student observes a wave travelling along a slinky spring. The wave causes the coils of the spring to move back and forth along the same direction as the wave is travelling.

(a) State the type of wave produced in the slinky. [1]

(b) Describe how the student could produce a transverse wave using the same slinky. [1]

Section B: Sound [10 marks]

6. A student claps her hands near a large wall and hears an echo 0.60 s later. The speed of sound in air is 340 m/s.

(a) Calculate the distance between the student and the wall. [2]

(b) Explain why the echo is quieter than the original sound. [1]

7. A loudspeaker produces a sound wave of frequency 680 Hz.

(a) Calculate the wavelength of this sound wave in air. (Speed of sound in air = 340 m/s) [2]

(b) The amplitude of the sound wave is increased. State and explain the effect on the loudness of the sound heard. [2]

8. Ultrasound is used in medical scanning to obtain images of internal organs.

(a) State the range of frequencies that are classified as ultrasound. [1]

(b) Explain why ultrasound, rather than audible sound, is suitable for medical scanning. [2]

9. A ship uses sonar to detect a shoal of fish. A pulse of sound is emitted and the echo is received 0.80 s later. The speed of sound in water is 1500 m/s.

(a) Calculate the distance of the shoal from the ship. [2]

10. A musician plays a note on a guitar. The string vibrates with a frequency of 440 Hz.

(a) State what determines the pitch of the note heard. [1]

(b) The musician tightens the string. Explain how this affects the pitch of the note produced. [2]

Section C: Light [20 marks]

11. A ray of light travels from air into a glass block. The angle of incidence in air is 45°. The refractive index of the glass is 1.5.

(a) State what is meant by the term "refractive index". [1]

(b) Calculate the angle of refraction in the glass. [2]

(c) On the diagram below, complete the path of the light ray as it enters the glass block and emerges from the opposite side. Label the angle of refraction. [2]

    Air          Glass          Air
    |              |              |
    |              |              |
    |   \          |              |
    |    \         |              |
    |     \        |              |
    |      \       |              |
    |       \      |              |
    +--------+-----+--------+-----+

12. A ray of light in water strikes the water-air boundary at an angle of incidence of 50°. The critical angle for the water-air boundary is 48°.

(a) Explain what is meant by "critical angle". [1]

(b) Describe and explain what happens to the light ray at the boundary. [2]

(c) State one application of total internal reflection. [1]

13. A converging lens of focal length 15 cm is used to form an image of an object placed 25 cm from the lens.

(a) Using the lens formula 1/f = 1/u + 1/v, calculate the image distance v. [2]

(b) State three characteristics of the image formed. [3]

14. A student uses a converging lens as a magnifying glass to examine a small insect.

(a) State where the insect must be placed relative to the lens to produce a magnified image. [1]

(b) Draw a ray diagram in the space below to show how the lens produces a magnified, virtual image of the insect. Label the object, image, and focal points. [3]

    (Use the space below for your ray diagram)

(c) The student replaces the lens with one of shorter focal length. Explain how this affects the magnification obtained. [2]

15. A ray of light strikes a plane mirror at an angle of incidence of 30°.

(a) State the angle of reflection. [1]

(b) State two characteristics of the image formed by a plane mirror. [2]

Section D: Electromagnetic Waves [10 marks]

16. State two properties that are common to all electromagnetic waves. [2]

17. A radio station broadcasts at a frequency of 100 MHz. The speed of electromagnetic waves in air is 3.0 × 10⁸ m/s.

(a) Calculate the wavelength of the radio waves. [2]

18. Infrared radiation is used in remote controls for televisions.

(a) State one other use of infrared radiation. [1]

(b) Explain why infrared radiation is suitable for use in remote controls. [1]

19. X-rays are used in medical imaging.

(a) State one property of X-rays that makes them suitable for medical imaging. [1]

(b) State one safety precaution that should be taken when using X-rays. [1]

20. A student investigates the refraction of light. She shines a ray of light from air into a transparent liquid at an angle of incidence of 60°. The angle of refraction is 40°.

(a) Calculate the refractive index of the liquid. [2]

END OF QUIZ

Check your answers carefully before submitting.

Answers

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O-Level Physics Quiz - Waves Sound Light - ANSWER KEY

Total Marks: 40

Section A: General Wave Properties [10 marks]

1. Wave on a rope

(a) Amplitude = 2.0 cm [1]

  • Accept: 2 cm
  • Mark: 1 mark for correct value with unit

(b) Wavelength = 40 cm [1]

  • Accept: 0.40 m
  • Mark: 1 mark for correct value with unit (distance between two consecutive crests/troughs)

(c) Speed calculation:

  • v = f × λ
  • v = 5.0 × 0.40 = 2.0 m/s
  • OR v = 5.0 × 40 = 200 cm/s [2]
  • Mark scheme:
    • 1 mark for correct formula v = fλ
    • 1 mark for correct answer with unit (2.0 m/s or 200 cm/s)

2. Ripple tank - deep to shallow water

(a) The speed decreases [1]

  • Mark: 1 mark for stating speed decreases

(b) Explanation:

  • v = fλ, and frequency (f) remains constant [1]
  • Since speed (v) decreases, wavelength (λ) must also decrease proportionally [1]
  • Mark scheme:
    • 1 mark for referencing v = fλ and constant frequency
    • 1 mark for linking decreased speed to decreased wavelength

3. Transverse vs longitudinal waves

Transverse waves:

  • Particles vibrate perpendicular to the direction of wave travel
  • Example: light waves / water waves / waves on a rope / any EM wave [1.5]

Longitudinal waves:

  • Particles vibrate parallel to the direction of wave travel
  • Example: sound waves / ultrasound / seismic P-waves [1.5]

Mark scheme:

  • 1 mark for correct description of transverse wave vibration direction
  • 0.5 mark for correct transverse example
  • 1 mark for correct description of longitudinal wave vibration direction
  • 0.5 mark for correct longitudinal example

4. Ripple tank wave calculation

(a) Speed calculation:

  • v = f × λ
  • v = 12 × 2.0 = 24 cm/s (or 0.24 m/s) [2]
  • Mark scheme:
    • 1 mark for correct formula v = fλ
    • 1 mark for correct answer with unit

(b) Ways to change speed:

  • Change the depth of the water [1]
  • Use a different liquid (change the medium) [1]
  • Mark: 1 mark each for any two valid methods

5. Slinky spring wave

(a) Type of wave: Longitudinal wave [1]

  • Mark: 1 mark for correct identification

(b) Producing a transverse wave:

  • Move one end of the slinky up and down (or side to side) perpendicular to the length of the spring [1]
  • Mark: 1 mark for describing perpendicular displacement of the end

Section B: Sound [10 marks]

6. Echo calculation

(a) Distance calculation:

  • Total distance travelled by sound = speed × time
  • Total distance = 340 × 0.60 = 204 m
  • Distance to wall = 204 ÷ 2 = 102 m [2]
  • Mark scheme:
    • 1 mark for calculating total distance (204 m)
    • 1 mark for dividing by 2 to get distance to wall (102 m)

(b) Explanation:

  • Sound energy spreads out over a larger area / some energy is absorbed by the wall and air [1]
  • Mark: 1 mark for any valid reason (energy spreading, absorption, or both)

7. Loudspeaker sound wave

(a) Wavelength calculation:

  • λ = v / f
  • λ = 340 / 680 = 0.50 m [2]
  • Mark scheme:
    • 1 mark for correct formula λ = v/f
    • 1 mark for correct answer with unit (0.50 m or 50 cm)

(b) Effect on loudness:

  • The sound becomes louder [1]
  • Explanation: A larger amplitude means more energy is transferred by the wave per unit time, resulting in greater loudness [1]
  • Mark scheme:
    • 1 mark for stating sound becomes louder
    • 1 mark for linking amplitude to energy transfer and loudness

8. Ultrasound

(a) Frequency range: Above 20 000 Hz (or above 20 kHz) [1]

  • Mark: 1 mark for correct lower bound (accept "above 20 kHz" or "above 20 000 Hz")

(b) Suitability for medical scanning:

  • Ultrasound has very short wavelengths, allowing it to produce detailed images of small structures [1]
  • Ultrasound can penetrate body tissues and reflect from boundaries between different tissues/organs, enabling imaging without harmful ionising radiation [1]
  • Mark scheme:
    • 1 mark for short wavelength / high resolution
    • 1 mark for penetration and reflection from tissue boundaries OR non-ionising/safe nature

9. Sonar calculation

(a) Distance calculation:

  • Total distance = speed × time = 1500 × 0.80 = 1200 m
  • Distance to shoal = 1200 ÷ 2 = 600 m [2]
  • Mark scheme:
    • 1 mark for calculating total distance (1200 m)
    • 1 mark for dividing by 2 to get distance to shoal (600 m)

10. Guitar string

(a) Pitch determinant:

  • The frequency of the vibrating string (or frequency of the sound wave) [1]
  • Mark: 1 mark for stating frequency

(b) Effect of tightening:

  • Tightening the string increases the tension, which increases the frequency of vibration [1]
  • A higher frequency produces a higher pitch [1]
  • Mark scheme:
    • 1 mark for linking increased tension to increased frequency
    • 1 mark for linking increased frequency to higher pitch

Section C: Light [20 marks]

11. Refraction in glass block

(a) Refractive index definition:

  • The ratio of the speed of light in vacuum (or air) to the speed of light in the medium [1]
  • Mark: 1 mark for correct definition (accept "n = c/v" or equivalent wording)

(b) Angle of refraction calculation:

  • n = sin i / sin r
  • 1.5 = sin 45° / sin r
  • sin r = sin 45° / 1.5 = 0.7071 / 1.5 = 0.4714
  • r = sin⁻¹(0.4714) = 28.1° (or 28°) [2]
  • Mark scheme:
    • 1 mark for correct substitution into n = sin i / sin r
    • 1 mark for correct answer (28° or 28.1°)

(c) Ray diagram:

  • Ray bends towards the normal on entering glass [0.5]
  • Angle of refraction labelled correctly [0.5]
  • Ray travels straight through glass [0.5]
  • Ray bends away from normal on exiting, emerging parallel to incident ray [0.5]
  • Mark: 2 marks total as indicated

12. Total internal reflection

(a) Critical angle definition:

  • The angle of incidence in the denser medium for which the angle of refraction in the less dense medium is 90° [1]
  • Mark: 1 mark for correct definition

(b) Description and explanation:

  • Total internal reflection occurs [1]
  • Explanation: The angle of incidence (50°) is greater than the critical angle (48°), so the light is completely reflected back into the water rather than being refracted into the air [1]
  • Mark scheme:
    • 1 mark for stating total internal reflection occurs
    • 1 mark for explaining that angle of incidence exceeds critical angle

(c) Application:

  • Optical fibres (in telecommunications/medicine) / endoscopes / periscopes using prisms / bicycle reflectors [1]
  • Mark: 1 mark for any valid application

13. Converging lens calculation

(a) Image distance calculation:

  • 1/f = 1/u + 1/v
  • 1/15 = 1/25 + 1/v
  • 1/v = 1/15 - 1/25 = (5 - 3)/75 = 2/75
  • v = 75/2 = 37.5 cm [2]
  • Mark scheme:
    • 1 mark for correct substitution into lens formula
    • 1 mark for correct answer with unit (37.5 cm)

(b) Image characteristics:

  • Real [1]
  • Inverted [1]
  • Magnified (larger than object) [1]
  • Mark: 1 mark each for any three correct characteristics (real, inverted, magnified/enlarged)

14. Magnifying glass

(a) Object position:

  • The insect must be placed between the lens and its focal point (i.e., at a distance less than the focal length from the lens) [1]
  • Mark: 1 mark for correct position (u < f)

(b) Ray diagram:

  • Correct lens symbol with principal axis [0.5]
  • Focal points (F and F') labelled on both sides [0.5]
  • Object (insect) placed between F and lens, labelled [0.5]
  • Two construction rays drawn correctly:
    • Ray parallel to axis, refracted through F' [0.5]
    • Ray through optical centre, undeviated [0.5]
  • Virtual image shown on same side as object, upright and magnified, labelled [0.5]
  • Mark: 3 marks total

(c) Effect of shorter focal length:

  • A lens with shorter focal length produces greater magnification when used as a magnifying glass [1]
  • Explanation: Magnification = 25/f (approx.) or the object can be brought closer to the lens while still being within the focal length, producing a larger virtual image [1]
  • Mark scheme:
    • 1 mark for stating magnification increases
    • 1 mark for valid explanation (shorter f means object can be closer / larger angular magnification)

15. Plane mirror

(a) Angle of reflection:

  • Angle of reflection = 30° [1]
  • Mark: 1 mark for correct value (equal to angle of incidence)

(b) Image characteristics:

  • Virtual [1]
  • Same size as object / laterally inverted / same distance behind mirror as object is in front [1]
  • Mark: 1 mark each for any two correct characteristics

Section D: Electromagnetic Waves [10 marks]

16. Properties of EM waves

  • They all travel at the same speed in a vacuum (3.0 × 10⁸ m/s) [1]
  • They are all transverse waves / they can travel through a vacuum / they transfer energy [1]
  • Mark: 1 mark each for any two correct properties

17. Radio wave calculation

(a) Wavelength calculation:

  • λ = v / f
  • λ = (3.0 × 10⁸) / (100 × 10⁶) = 3.0 m [2]
  • Mark scheme:
    • 1 mark for correct formula λ = v/f
    • 1 mark for correct answer with unit (3.0 m)

18. Infrared radiation

(a) Use of infrared:

  • Thermal imaging / heating / cooking / night vision / data transmission (optical fibres) [1]
  • Mark: 1 mark for any valid use

(b) Suitability for remote controls:

  • Infrared is invisible to the human eye / does not interfere with visible light / can be modulated to carry information / is easily detected by electronic sensors [1]
  • Mark: 1 mark for any valid reason

19. X-rays

(a) Property for medical imaging:

  • X-rays can penetrate soft tissue but are absorbed by bone / have short wavelengths enabling high resolution [1]
  • Mark: 1 mark for any valid property

(b) Safety precaution:

  • Limit exposure time / use lead shielding / stand behind a protective screen / wear a dosimeter badge [1]
  • Mark: 1 mark for any valid precaution

20. Refractive index calculation

(a) Refractive index calculation:

  • n = sin i / sin r
  • n = sin 60° / sin 40°
  • n = 0.8660 / 0.6428 = 1.35 (or 1.3) [2]
  • Mark scheme:
    • 1 mark for correct formula and substitution
    • 1 mark for correct answer (1.35 or 1.3)

END OF ANSWER KEY