P1 Revision Booklet

Wave basics, Reflection and Refraction

Medium (Grade C)

Q1.          Diagram 1 shows a longitudinal wave being produced in a stretched spring.

(a)      A longitudinal wave has areas of compression and areas of rarefaction.
Mark with the letter C, one area of compression shown in Diagram 1.
(1)

(b)     Diagram 2 shows the apparatus a teacher uses to demonstrate that sound can be reflected.

(i)     Using a ruler, draw on Diagram 2 to show how sound from the loudspeaker is reflected by the sheet of metal to the sound sensor.
(2)

(ii)     The teacher replaced the sheet of metal with a sheet of glass.
When he did this, the reading on the sound level meter went down.
Suggest why.
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(1)

(iii)    The teacher changed the output from the loudspeaker to increase the amplitude of the sound wave produced.
What effect, if any, does this increase of amplitude have on the loudness of the sound?
Draw a ring around the correct answer.
 
makes the sound quieter	does not change the loudness of the sound	makes the sound louder	

(1)

(iv)    The loudspeaker produces a sound wave at a frequency of 850 Hz. The wavelength of the sound wave is 0.4 m.
Calculate the speed of the sound wave.
Use the correct equation from the Physics Equations Sheet.
Show clearly how you work out your answer.
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                   Speed = ...................................................................... m/s
(2)

(c)     Music concerts are sometimes performed in sports halls. The concerts can be spoilt because of the sound reflected from the floor and walls.
What word is used to describe a reflected sound?
........................................................................................................................
(1)

(d)    The graph shows how the percentage of sound reflected from the floor and from the walls of a large room can be reduced by carpets and by curtains.

(i)      Over which range of frequencies do curtains reduce the percentage of sound reflected the most?
Tick () two boxes.
 
from 250 Hz to 750 Hz		
from 750 Hz to 1250 Hz		
from 1250 Hz to 1750 Hz		

(1)

(ii)     The manager of a sports hall plans to use the hall for regular music concerts. He has enough money to buy either carpet or curtains, but not both.
To improve the sound an audience hears, it would be better to hang curtains on the walls rather than laying a carpet over the floor.
Use the data in the graph to explain why.
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(2)
(Total 11 marks)
 Q2.          The diagram shows some waves travelling along a rope.

(a)     Show on the diagram
(i)      the wavelength of one of the waves 
(2)
(ii)     the amplitude of one of the waves 
(2)

(b)     The waves shown on the diagram were produced in two seconds.
          What is the frequency of the waves?
.....................................................................................................................................
(2)
(Total 6 marks)
 Q3.          The diagram shows oscilloscope traces of four waves, A, B, C and D. All four waves are drawn to the same scale.

          Which wave has:
(a)     the longest wavelength; ..........
(b)     the greatest amplitude; ..........
(c)     the highest frequency? ..........
(Total 3 marks)
 
Q4.          The diagram shows a wave travelling along a rope.

(a)     On the diagram:
(i)      show the wavelength and label it W;
(ii)     show the amplitude and label it A.
(2)

(b)     The wavelength of the wave is 0. I m. Its frequency is 2 Hz.
          Calculate the speed of the wave. Show clearly how you work out your answer and give the unit.
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Speed of wave .................................................................
(3)
(Total 5 marks)
Q5.          Water waves can be made by vibrating a wooden bar up and down in a tray of water.
The bar moves up and down at a frequency of 5 hertz.

(a)     Calculate the speed, in cm/s, of the water waves.
Write down the equation you use and then show clearly how you work out your answer.
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Wave speed = ................................... cm/s
(3)

(b)     The graph shows how the speed of deep ocean waves depends on the wavelength of the waves.

Use the graph to predict a speed for waves with a wavelength of 140 m.
Show clearly how you have used the graph to work out your answer.
Speed of waves = .................................. m/s
(2)
(Total 5 marks)
 Q6.          (a)     The diagrams below show rays of light striking a mirror and a perspex block.

          Complete the paths of the three rays of light on the diagrams to show the rays leaving the mirror and the perspex block.
(4)

(b)     The diagram below shows a beam of light striking a perspex block.

(i)      Continue the paths of the rays AB and CD inside the perspex block.

(ii)     Draw the wavefronts of the beam of light in the perspex.

(iii)     Explain why the beam behaves in the way you have shown.
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(7)

(c)     The diagram below shows a ray of light striking a perspex-air surface from inside the perspex. The critical angle is 45º.

          Draw the path of the ray after it reaches the perspex-air boundary.
(2)
(Total 13 marks)
 
Q7.          (a)     The diagrams show rays of light. Each ray strikes a surface of a glass block.

(i)      On the diagram draw the path of each ray through the glass block and out into the air again.
(ii)     Label another angle on the diagram which is equal to the angle marked X. Label this angle Y.
(4)

(b)     The diagrams show two beakers. Both beakers have a drawing pin inside as shown.

          The first beaker is empty. The eye cannot see the drawing pin.
The second beaker is full of water and the eye can see the drawing pin.

          Explain how the eye is able to see the drawing pin in the second beaker. You may add to the diagram if it helps your answer.
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(3)
(Total 7 marks)
 Q8.          Most young people can hear sounds in the frequency range 20 Hz to 20 000 Hz.
(a)     Tick the box beside the statement which best describes frequency.
the maximum disturbance caused by a wave                            
the number of complete vibrations per second                           
the distance between one crest of a wave and the next one      
the distance travelled by a wave in 1 second                              
(1)

(b)     Diagram X shows a trace on an oscilloscope screen.

(i)      Draw a trace on diagram Y which has a higher frequency than that shown in 
diagram X.

(ii)     Draw a trace on diagram Z which has a larger amplitude than that shown in 
diagram X.
(2)

(c)     Choose words from the list below to complete the following sentences.
higher             louder             lower               quieter

(i)      A musical note with a high frequency sounds ........................................ than one with a low frequency.

(ii)     A noise of small amplitude sounds ........................................ than one with large amplitude.
(2)
(Total 5 marks)

 

Wave basics, reflection and refraction-Mark scheme
M1.          (a)     letter C clearly marking a compression
accept C at any point in a compression
if more than one letter C marked 
all must be correct
1

(b)     (i)      straight continuous line drawn from loudspeaker to metal to sound sensor
judge by eye
1
angle I = angle R
judge by eye
ignore any arrows on lines
1

(ii)     less sound reflected
accept energy for sound
or
(some) sound passes through the glass
accept (some) sound absorbed by the glass
1

(iii)    makes the sound louder
1
(iv)    v = f × λ
340
allow 1 mark for correct substitution
ie 850 × 0.4
provided no subsequent step shown
2

(c)     echo
1
(d)     (i)      from 250 Hz to 750 Hz
1

(ii)     curtains reduce (percentage of) sound reflected more (than carpet)
accept curtains absorb more sound (than carpet)
1
for all frequencies (shown)
accept for both marks an answer in terms of walls having a larger (surface) area to reflect sound and curtains reducing the amount of reflected sound more (than carpet)
answers less noisy or walls / curtains have a larger area gain 1 mark only
do not accept curtains are cheaper
1
[11]
 M2.          (a)     (i)      a horizontal distance indicated and labelled
gains 1 mark
         but
horizontal distance indicated between identical points on
adjacent waves (to within 3-4mm) and labelled
gains 2 marks
2

(ii)     peak ↔ trough indicated*
gains 1 mark
         but
peak / trough ↔ mean indicated*
         (* to within 1-2mm either end)
gains 2 marks
(allow 1 mark if both lines unlabelled or 2 marks if both lines 
accurately drawn and unlabelled)
2

(b)     •        1.5
•        hertz / Hz          or          (waves / cycles) per second
for 1 mark each
(do not allow wavelength / hertz per second)
2
[6]
 M3.          (a)     D
1

(b)     C
1

(c)     B
1
[3]
 M4.          (a)     any two successive peaks labelled W
accept any 2 points on same part of adjacent waves
correct by eye
1
          half ‘height’ of wave labelled A
correct by eye
N.B. at least one of the answers must be labelled
1

(b)     0.2
correct answer with no working = 2
allow 1 mark for s = f x w or correct working i.e., 2 × 0.1
N.B. correct answer from incorrectly recalled relationship = 0
2
          m/s (unit)
independent mark do not allow mps or mHz
1
[5]
 M5.          (a)     40 (cm/s)
correct answer
an answer 0.4 m/s gains full credit
if answer is incorrect
allow 1 mark for correct wavelength λ = 8 cm
or 
allow 2 marks for correct substitution into the correct equation, ie. V = 5 × 8
or
allow 2 marks for clearly stated wrong wavelength correctly substituted into correct equation and correctly calculated, ie
λ   = 16 cm/s
V  = 5 × 16
     = 80
3

(b)     line extended following pattern
1
14 m/s
accept their numerical value, if not 14,
provided the first mark has been awarded
1
[5]
 M6.          (a)     Reflection correct
Normal incidence correct in and out
Correct refraction in
Parallel ray out
each for 1 mark
4

(b)     (i)      Each ray correctly refracted in
1 + 1 = 2
7

(ii)     Wavefronts perp sides
Wavefronts closer
(Cannot score wavefront marks if refracted rays clearly wrong)

(iii)     Speed reduces
Starting at B
Then D
each for 1 mark

(c)     TIR correct
gets 2 marks
Else rough reflection
gets 1 mark
2
[13]

 

M7.          (a)     (i)      Ignore arrows on rays
perpendicular rays goes straight in and out
other ray refracts towards normal (not along)
emerges parallel incident ray (by sight) if refraction correct (ignore reflections)
for 1 mark each
3

(ii)     emergent angle marked Y if emerges parallel to right of normal
for 1 mark
1

(b)     straight ray to water surface refracts/bends
straight to eye/towards surface on right image correctly shown
or states the same mark prose only of diagram incomplete
any 3 for 1 mark each
3
[7]
M8.          (a)     number of complete vibrations per second
for 1 mark
1

(b)     (i)      correct trace (more waves), ignore amplitude
for 1 mark
1
(ii)     correct trace (higher amplitude), ignore frequency
for 1 mark
1

(c)     (i)      higher
for 1 mark
1
(ii)     quieter
for 1 mark
1
[5]