WavesIB MYP Sciences: Topic test

1. 1
   A family in Bogotá uses a microwave oven to heat food, an infrared remote control for the television, and a mobile phone that connects to a radio mast.

   (a)

   Which of the three types of radiation used in the home has the highest frequency?

   [1 mark]

   • ARadio waves from the mast
   • BMicrowaves in the oven
   • CInfrared from the remote control
   • DAll three have the same frequency

   (b)

   What is the speed of all three types of radiation in a vacuum?

   [1 mark]

   • A3.0 × 10⁸ m/s
   • B3.4 × 10² m/s
   • C3.0 × 10⁶ m/s
   • D3.0 × 10¹⁰ m/s

   (c)

   The door of the microwave oven contains a metal mesh. Explain why this makes the oven safer to use.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student in Melbourne rings an electric bell inside a sealed glass bell jar. A pump gradually removes the air from the jar while the bell keeps ringing.

   (a)

   What does the student hear as the air is removed?

   [1 mark]

   • AThe bell gets louder
   • BThe bell gets quieter and almost cannot be heard
   • CThe pitch of the bell rises
   • DThere is no change in the sound

   (b)

   What is the main reason for this change?

   [1 mark]

   • ASound is a transverse wave
   • BThe bell stops vibrating
   • CThe sound waves are absorbed by the glass
   • DThere are fewer air particles to pass on the vibrations

   (c)

   Describe how the air particles move when a sound wave passes through the air before the pump is switched on.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student in a gym in Hanoi stretches a long rope along the floor and shakes one end from side to side 2.5 times each second. This makes waves of wavelength 0.80 m travel along the rope.

   (a)

   Calculate the speed of the waves along the rope.

   [3 marks]

   (b)

   The student now shakes the rope twice as fast. The speed of the waves along the rope stays the same. Calculate the new wavelength and the period of the waves.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A telecommunications company in the Philippines plans to connect a group of small islands to the internet. It can either lay glass optical fibre cables along the sea floor, which carry data as pulses of infrared light, or build radio towers that send the data as radio waves through the air. Laying the cable would need special ships and would cross a coral reef.

   (a)

   Describe and explain how an optical fibre carries pulses of light along its length without the light escaping.

   [6 marks]

   (b)

   Discuss the advantages and disadvantages of using optical fibre rather than radio towers to connect the islands. Give a justified conclusion.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A physics teacher in Galway uses a glass prism to split a narrow beam of white light from a torch into a band of colours on a screen.

   (a)

   Which colour of light is refracted the most by the prism?

   [1 mark]

   • ARed
   • BGreen
   • CYellow
   • DViolet

   (b)

   Why does the prism separate the white light into different colours?

   [1 mark]

   • ADifferent colours travel at different speeds in glass, so they are refracted by different amounts
   • BThe glass adds colour to the white light
   • CThe prism absorbs some colours and gives out others
   • DWhite light is reflected from the glass surface

   (c)

   Describe what happens to the speed and direction of a ray of light when it passes from air into the glass of the prism at an angle.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A village lies in a deep valley in the Bolivian Andes behind a high mountain ridge. Long-wave radio signals with a wavelength of about 1500 m reach the village, but FM radio signals with a wavelength of about 3 m are blocked by the ridge.

   (a)

   Which process makes the long-wave radio waves spread around the mountain ridge into the valley?

   [1 mark]

   • AReflection
   • BDiffraction
   • CDispersion
   • DTotal internal reflection

   (b)

   Waves also spread out when they pass through a gap. When is this diffraction greatest?

   [1 mark]

   • AWhen the gap is much larger than the wavelength
   • BWhen the gap is completely closed
   • CWhen the gap is about the same size as, or smaller than, the wavelength
   • DWhen the gap size has no link to the wavelength

   (c)

   Explain why the long-wave signals reach the village but the FM signals do not.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A bat flying in a cave in Borneo finds its way by echolocation. It gives out a short pulse of ultrasound with a frequency of 60 kHz. The speed of sound in the air of the cave is 340 m/s.

   (a)

   Calculate the wavelength of the bat's ultrasound.

   [3 marks]

   (b)

   The bat hears the echo from a wall 0.050 s after it gives out the pulse. Calculate the distance from the bat to the wall. Explain why humans cannot hear the bat's pulse.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A guitar maker in Seville wants to know how the length of a vibrating string affects the pitch of the note it makes. She has a string stretched between two fixed points, a movable bridge that changes the vibrating length, a ruler and a smartphone app that shows the frequency of a sound.

   (a)

   Design an investigation to test how the vibrating length of the string affects the frequency of the note. Include a hypothesis with a reason, the variables and a precaution.

   [6 marks]

   (b)

   Her results are: 0.80 m gives 110 Hz, 0.40 m gives 220 Hz and 0.20 m gives 440 Hz. She concludes that the frequency is inversely proportional to the length. Evaluate her conclusion.

   [6 marks]

   Total for question 8: 12 marks

End of questions