Exam-style Questions: Uses of Waves

1. The diagram shows a representation of a sound wave on the screen of an oscilloscope. a) Name a device that could have been used to capture the sound wave and turn it into the electrical signal for the oscilloscope.

(1 mark)

b) How would the trace change if the frequency of the sound increased?

(2 marks)

c) Each square represents 2 x 100ths of a second.

How long does it take for one wave to happen?

(2 marks)

d) How many waves happen in one second?

(1 mark)

e) What is the frequency of the sound wave?

(2 marks)

f) If sound travels at a speed of 330 m/s, then what is the wavelength of the wave?

(2 marks)

(Marks available: 10)

Answer outline and marking scheme for question: 1

a) Microphone.

(1 mark)

b) The wave should become more compressed but the wave height remains the same.

(2 marks)

c) 0.08 s

(2 marks)

d) 12.5 waves

(1 mark)

e) 12.5 Hz

(2 marks)

f Wavelength = wave speed / frequency

Wavelength = 330 / 12.5 = 26.4 m

(2 marks)

(Marks available: 10)

2. a) A ray of light approaches the rear view mirror in a car at an angle of 33 degrees to the normal line. What is the normal line?

(2 marks)

b) What would be the size of the angle of reflection?

(1 mark)

c) If the mirror is moved to position marked X how would the path of the reflected ray of light be effected?

(1 mark)

d) What would the driver see?

(1 mark)

e) If the driver wished to check her make up in what direction might she adjust the rear view mirror?

(1 mark)

f) This diagram shows the arrangement of two mirrors in a periscope. Copy and complete the diagram to show the ray of light passing through the periscope.

(2 marks)

g) State a use for a periscope.

(1 mark)

h) What other optical device could be used instead of mirrors in a periscope?

(1 mark)

(Marks available: 10)

Answer outline and marking scheme for question: 2

a) Imaginary line at right angles to the mirror from which all angles are measured.

(2 marks)

b) 33 degrees.

(1 mark)

c) The ray would reflect upwards.

(1 mark)

d) The driver would see the ceiling.

(1 mark)

e) Tilt the top downwards.

(1 mark)

f) Light rays at 45 degrees to mirrors, with direction marked correctly.

(2 marks)

g) Any valid use, for example, looking over walls. Driver seeing upper deck on double decker buses.

(1 mark)

h) Prisms.

(1 mark)

(Marks available: 10)

3. Some waves approach a beach. a) Why do the waves get closer as the waves approach the beach?

(2 marks)

b) If a large rock is placed at X, then what will happen to the waves that pass it?

(2 marks)

c) Nearby the waves pass through a gap between two pier supports. Describe what happens to the waves as they pass through.

(2 marks)

d) Ashia has a glass of lemonade and she notices that the straw looks crooked. Use ideas of refraction to explain this.

(2 marks)

e) Name two optical devices that work because of refraction.

(2 marks)

(Marks available: 10)

Answer outline and marking scheme for question: 3

a) They slow down because the water is getting shallower - refraction.

(2 marks)

b) Waves diffract as they pass curving around into the space behind the rock.

(2 marks)

c) Waves diffract as they go between the supports spreading into a curved wave.

(2 marks)

d) Light rays from the straw in the air come straight to the eye. Rays from the straw in the water are refracted as they leave the water. This change of direction means they appear to come from somewhere else.

(2 marks)

e) Lens, Prism.

(2 marks)

(Marks available: 10)

4. The diagram shows the path of light rays entering the eye of a fish. a) Why does the ray P bend as it enters the water?

(1 mark)

b) What has happened to ray Q as it entered the water?

(1 mark)

c) What is the name of the effect shown by rays N and S?

(1 mark)

d) This effect is used in Fibre Optic communication. Why does the ray of light not escape the optical fibre?

(2 marks)

e) Fibre optic cables are replacing copper wires in telecommunication links.

Give two advantages fibre optic cables have over copper wire.

(2 marks)

f) Give two other uses for fibre optics.

(2 marks)

(Marks available: 9)

Answer outline and marking scheme for question: 4

a) It refracts - a decrease in speed makes it bend inwards.

(1 mark)

b) It slows but does not deviate because it met the boundary at right angles.

(1 mark)

c) Total internal reflection.

(1 mark)

d) It meets the boundary at an angle greater than the critical angle.

(2 marks)

e) Greater data capacity, fewer signal repeaters, smaller and lighter, cheaper raw materials, more secure data transmission.

(2 marks)

f) Endoscopy, intranet links, novelty items.

(2 marks)

(Marks available: 9)

5. Here is a diagram of the electromagnetic spectrum: a) What are the missing parts of the electromagnetic spectrum labeled P and Q?

(2 marks)

b) Which end of the spectrum has the longest wavelength?

(1 mark)

c) Which end of the spectrum has the highest energy?

(1 mark)

d) Give one use for the infrared.

(1 mark)

e) Name two detectors of visible light.

(2 marks)

f) Ultra Violet radiation is present in sunlight.

In what way is the Ultra Violet harmful to humans?

(1 mark)

g) How can the risks be reduced?

(2 marks)

(Marks available: 10)

Answer outline and marking scheme for question: 5

a) P-microwaves, Q-xrays.

(2 marks)

(1 mark)

c) Gamma rays.

(1 mark)

d) Heat therapies, thermal imaging cameras.

(1 mark)

e) The eye, photographic film, ldr, photo voltaic cell.

(2 marks)

f) Causes sunburn and skin cancers.

(1 mark)

g) Wearing sunscreen and limiting time in the sun.

(2 marks)

(Marks available: 10)

6. During pregnancy the unborn foetus is monitored using Ultrasound. a) What is Ultrasound?

(1 mark)

b) Name one animal that might hear ultrasound.

(1 mark)

c) Why would the doctor not use x-rays to monitor the unborn child?

(2 marks)

Ultrasound can also be used to detect shoals of fish, it can be called sonar. A pulse of ultrasound is sent out from the boat an echo is heard 0.3 seconds later.

d) What is an echo?

(1 mark)

e) The speed of ultrasound in water is 1500 m/s.

Why does ultrasound (and sound) travel faster in water than in air?

(2 marks)

f) Calculate the depth of the shoal of fish.

(3 marks)

(Marks available: 10)

Answer outline and marking scheme for question: 6

a) Sound vibrations too high for humans to hear.

(1 mark)

b) Bats, dogs...

(1 mark)

c) X-rays would harm the developing foetus.

(2 marks)

d) An echo is wave a sound wave reflects off something.

(1 mark)

e) The particles in a liquid are closer allowing better interaction between particles in the longitudinal wave.

(2 marks)

f) Speed = distance / time. Distance = speed x time.

Distance = 1500 x 0.3 = 450 m

Half this to get depth.

Depth = 225 m.

(3 marks)

(Marks available: 10)

7. a) What does a seismometer measure?

(1 mark)

b) Name the scale that describes earthquake intensity.

(1 mark)

c) An earthquake creates S-waves and P-waves.

Which of these is a longitudinal wave and which is a transverse wave?

(2 marks)

d) How is the motion different in a longitudinal and a transverse wave?

(2 marks)

e) Which of S-waves and P-waves can travel through liquids?

(1 mark)

f) On the opposite side of the earth to the earthquake, only one type of wave is detected.

Which type is detected?

(1 mark)

g) What does this tell us about the core of the earth?

(2 marks)

(Marks available: 10)

Answer outline and marking scheme for question: 7

a) Vibrations in the earth, earthquakes.

(1 mark)

b) Reichter scale

(1 mark)

c) S-waves are transverse and p-waves are longitudinal.

(2 marks)

d) Transverse motion has particles oscillating across the direction of travel, whereas in longitudinal the oscillations are parallel to the direction of travel.

(2 marks)

e) P-waves.

(1 mark)

f) P-waves.

(1 mark)

g) The core is liquid as the waves that get through can go through liquid.

(2 marks)

(Marks available: 10)