P1 Revision Booklet

Ultrasound

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?
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(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 an ultrasound monitor being used to scan a fetus.

          The table shows the velocity of ultrasound waves in different tissues of the fetus.
 
Tissue 	Velocity of ultrasound in m/s 	
Amniotic fluid
(liquid surrounding fetus) 	1540 	
Bone 	3080 	
Kidney 	1561 	
Liver 	1549 	
Muscle 	1585 	

          Explain why we are able to see the different parts of the fetus in an ultrasound scan. You may use information from the table in your answer.
          To gain full marks in this question you should write your ideas in good English. Put them into a sensible order and use the correct scientific words.
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(Total 4 marks)
 Q3.          (a)     Explain what an ultrasound wave is.
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(2)
(b)     Ultrasound waves can be used to clean jewellery.
One method is to put the jewellery in a bath of cleaning fluid which contains an electronic oscillator. The electronic oscillator generates ultrasound waves in the cleaning fluid.
Suggest how these waves clean the jewellery.
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(2)

(c)     Ultrasound is used for pre-natal scanning. This is much safer than using X-rays. However, doctors were only sure it was safe after experiments on mice.
Explain whether or not you think that these experiments were justified.
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(2)
(Total 6 marks)

 

Q4.          (a)     Sound travels through air, water and glass at different speeds. Through which of these materials does sound travel:
          the fastest; .............................................
          the slowest? ...........................................
(2)
          Give a reason for your choice of answers.
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(1)

(b)     The bar chart shows the frequencies of sound which different animals can make and can hear.

(i)      Which of the animals can make sounds which are beyond their own hearing range?
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(1)

(ii)     What name is given to the sounds which a cat can hear but a human cannot?
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(1)

(c)     The diagram shows a trawler searching for a shoal of fish. Pulses of high frequency sound emitted from the trawler are reflected back to the trawler. The pulses are displayed on a cathode ray oscilloscope.

          Complete the diagram below to show the pattern seen on the cathode ray oscilloscope as the trawler passes over the shoal of fish.

(2)
(Total 7 marks)
 Q5.          (a)     This information is from a science magazine.
 
Electronic systems can be used to produce ultrasonic waves.
These waves have a frequency higher than the upper limit for hearing in humans.	

          Complete the sentence by choosing the correct number from the box.
 
             20                    2000                 20 000                200 000	

          The upper limit for hearing in humans is a frequency of ............................................ Hz.
(1)

(b)     An electronic system produces ultrasound with a frequency of 500 kHz.
          What does the symbol kHz stand for?
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(1)

(c)     (i)      State one industrial use for ultrasound.
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(1)

(ii)     State one medical use for ultrasound.
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(1)

(d)     An ultrasound detector is connected to an oscilloscope.
          The diagram shows centimetre squares on an oscilloscope screen. Each horizontal division represents 2 microseconds.

          Calculate the time, in microseconds, between one peak of one ultrasound pulse and the peak of the next.
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Time = .............................. microseconds
(1)

(e)     Ultrasounds are partially reflected when they reach a boundary between two different media.
          The time taken for the reflection from the boundary to reach the detector can be seen
from the screen.
          What can be calculated from this time interval?
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(2)

(f)      Explain what action scientists should take if they find evidence that ultrasonic waves may be harmful to human health.
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(2)
(Total 9 marks)
 Q6.          (a)     A microphone connected to an oscilloscope picks up the sound from a siren. The trace produced on the oscilloscope screen is shown below.

          Describe how the wave changes as it goes across the screen from left to right (→).
          To gain full marks in this question you should write your ideas in good English. Put them into a sensible order and use the correct scientific words.
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(3)

(b)     An African bat produces a sound wave with a frequency of 212 kHz and a wavelength of 0.0016 m.
(i)      The sound made by the bat is above the limit of human hearing.
What name is given to this type of sound?
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(1)

(ii)     Write down the equation that links frequency, wavelength and wave speed.
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(1)

(iii)     Calculate the speed of this sound wave through the air. Show clearly how you work out your final answer.
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Wave speed = ............................... m/s
(3)
(Total 8 marks)
 Q7.          (a)     What is ultrasound?
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(1)

(b)     The picture shows a pregnant woman having an ultrasound scan and the image produced by the scan.

          To produce the image, a very narrow beam of ultrasound pulses is fired into the mother’s body. The reflected pulses are used to build up the image of the unborn baby.

(i)      Why is it important to have a very narrow beam of ultrasound waves?
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(1)
(ii)     Why is it possible to produce a very narrow beam with ultrasound but not with normal sound waves?
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(1)

(iii)     The image produced by ultrasound is not as clear as an image produced by X-rays. Why is ultrasound used for looking at unborn babies rather than X-rays?
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(1)

(iv)    Give two important pieces of information about an unborn baby which can be gained from the image produced by an ultrasound scan.
1 .....................................................................................................................
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2 .....................................................................................................................
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(2)
(Total 6 marks)
 Ultrasound-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
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 M2.          Quality of written communication
          correct use of three scientific terms from speed / velocity, reflection,
density, time, boundary
1
          any three from:
          different tissues have different densities
          ultrasound travels at different speeds / velocities in different tissues
          reflection
accept bouncing back
          from tissue boundaries
          time taken to return
3
[4]
 M3.          (a)     sound / mechanical / longitudinal (wave )
1

any one from:
•        above 20 000 hertz / 20kHz
•        above (human) audible range
•        cannot be heard by humans
1

(b)     either
particles / molecules / fluid vibrate(s) (1)
(and) knock particles of dirt off the jewellery (1)
or
by the process of cavitation (1)
accept ‘formation and collapse of tiny bubbles’
which breaks up / releases dirt from the surface (1)
2

(c)either both pro
or both con
or one of each
either
two appropriate points gain 1 mark each
or
one appropriate point (and) appropriate qualification / amplification
examples
other mammals (sufficiently) similar to humans (1)
so results appropriate (1)
unethical to experiment on humans (1)
so it is better to experiment on mice (1)
knowledge / techniques will benefit humans (1)
and also other animals (1)
experiments were justified because ultrasound has proved useful (1)
2
[6]
 M4.          (a)     glass
1
          air
must be in correct order
1

closer the particles faster the speed
answer must show a comparison
or
          particles in glass closest in air furthest apart
accept the denser the material the faster the sound travels
or
          sound travels faster in solids than gases
incorrect explanation negates credit
1

          (b)     (i)      grasshopper
(ii)     ultrasound
accept ultrasonic
1

(c)     all of reflected pulse closer than given in original diagram
accept a cluster of pulses ignore a reflected pulse in original position any pulse drawn to right of original negates credit
1
          reflected pulse smaller than emitted but greater than 1 square high
accept cluster of pulses provided one part fulfils height criteria
2
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 M5.          (a)     20000
accept any unambiguous indication
1
(b)     kilohertz
credit misspellings
credit ‘1000 hertz’ or ‘1000 Hz’
accept 1000 oscillations/beats/waves per second
1

(c)     (i)      cleaning (e.g. something delicate such as a watch)
or quality control/flaw detection
credit any appropriate extra Specification response
e.g. sonar
1
(ii)     pre-natal (scanning)
do not credit just ‘scanning’/medical scanning/ scanning a baby
credit any appropriate extra Specification response
e.g. destruction of (kidney) stones or cleaning teeth
1

(d)     8 (μs)
1
(e)     distance (1)
          between the boundary and the detector (1)
accept ‘between the boundary and the source’
accept any correct use of speed = distance/time
2

(f)      examples
          publish/tell doctors/the public (1) ... their evidence/results/research/data (1)
          carry out more research/tests (1) ... to make sure/check reliability (1)
allow a wide variety of appropriate responses
valid point (1) appropriate example/qualification/expansion/etc. (1)
allow just ‘stop using them/ultrasonic waves’ (1)
allow using them (only) for industrial purposes (1)
2
[9]
 M6.          (a)     any two from:
•        amplitude decreasing
accept siren / sound getting quieter
do not accept sound decreases
•        wavelength increasing
•        frequency decreasing
accept pitch decreasing
ignore reference to transverse wave
ignore reference to speed
contradictory statements within each point lose the mark
2
          Quality of written communication
all emboldened terms in candidate’s answer used correctly
1

(b)     (i)      ultrasound or ultrasonic
1

(ii)     wave speed = frequency × wavelength
accept speed / velocity for wave speed
accept v = f  λ
do not accept w for λ
do not accept s for v
accept
 
provided subsequent calculation
shows a correct method
1

(iii)     339.2 or 340 or 339
allow 1 mark for using 212 000
allow 1 mark for correct substitution
an answer of 0.3392 or 0.34 or 0.339 gains 1 mark only
award full credit for a correct numerical answer with the unit changed to km/s
3
[8]
 M7.          (a)     sound with a frequency above audible
do not accept answer in terms of λ
do not accept sound which cannot be heard unless obvious from context
accept above 20 kHz
1

          (b)     (i)      to show detail or to give a clear image/picture
accept the generators or transducers can be small
accept so the beam does not spread out/beam in focus
not ‘good picture’
1

(ii)     (much) smaller wavelength
allow higher frequency/pitch
1
(iii)     no damage to living cells (provided low power)
accept the converse
accept no damage to baby or not dangerous to baby
1
(iv)    any two forms
sex
stage of development
or specific examples
abnormalities
general health
potential problems (at birth)
accept specific examples e.g. umbilical cord around neck
size of head
accept multiple births
2
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