P1 Revision Booklet

EM Spectrum

Medium (Grade C)

Q1.          (a)     Electromagnetic waves have many uses. The diagram shows two ways of sending information using electromagnetic waves.

(i)      What type of wave is used to send information to and from satellites?
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(1)

(ii)     What property of this type of wave makes it suitable for satellite communications?
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(1)

(b)     The diagram shows two types of signal that can be used to send information. One of the signals is an analogue signal. The other is a digital signal.

Describe the differences between an analogue signal and a digital signal.
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(2)

(c)     Different frequency radio waves travel different distances through the atmosphere before being reflected.

Use the information in the diagram to describe the connection between the frequency of a radio wave and the distance the radio wave travels through the atmosphere before it is reflected.
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(1)

(d)     Electromagnetic waves travel at a speed of 300 000 000 m/s.
A radio station transmits waves with a wavelength of 20 metres.
Use the equation in the box to calculate the frequency, in kilohertz (kHz), of these waves.
 
wave speed   =   frequency   ×   wavelength	

Show clearly how you work out your answer.
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                                          Frequency = .................................................. kHz
(2)
(Total 7 marks)

 
Q2.          (a)     Scientific research carried out in 13 countries has tried to find out if there are any links between using a mobile phone and developing different types of cancer.
About 13 000 people, half with cancer and half in good health, were interviewed about their mobile phone use.
(i)      Suggest why people in good health were interviewed.
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(1)

(ii)     Interviewing 13 000 people gave the researchers a large sample size.
Give one advantage, in any research project, of having a large sample size rather than a small sample size.
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(1)

(b)     The following information was included in a newspaper article about the research project.
 
•         It may be difficult to prove there is a link simply by asking people how much they use a mobile phone. People’s memories are not always accurate.
•         Scientists in Israel found that people who use a mobile phone a lot are 50% more likely to develop a cancer on the salivary gland just in front of the ears.
•         The cost of the research, £20 million, has been partly paid for by mobile phone companies.
•         No children were included in the research.	

(i)      Draw a ring around the correct answer to complete the following sentence.
 
Using children in scientific research raises	environmental
ethical
social	issues.	

(1)

(ii)     Suggest two reasons why some people are concerned that the research was partly paid for by mobile phone companies.
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(2)

(iii)     In Germany, mobile phones that emit very low levels of radiation are marked with a special symbol.
Explain why low emission mobile phones should be marked in this way.
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(2)
(Total 7 marks)
 Q3.          The diagram below shows the range of wavelengths and frequencies for all the types of radiation in the electromagnetic spectrum.
          X‑rays, which have frequencies in the range 1018–1021 Hz are already marked on the diagram.

          Complete the diagram by adding the following: 
(a)     gamma radiation, which has shorter wavelengths than X‑rays;
(b)     radio waves which have wavelengths longer than 0.1m;
(c)     the visible spectrum which has wavelengths from 400 nm (violet) to 700 nm (red);
(d)     ultraviolet radiation (i.e. radiation with a higher frequency than violet light);
(e)     microwaves which have a shorter wavelength than radio waves and infrared radiation which has a higher frequency than microwaves;
(f)      an FM radio programme on 92MHz. (Show this with an arrow ®)
(Total 7 marks)

 
Q4.          Microwave ovens can be used to heat many types of food.

(i)      Describe, in as much detail as you can, how microwaves heat food.
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(2)

(ii)      Microwaves have a frequency of 10 000 million Hz. Their wavelength is 0.03 m.
          Calculate the speed of microwaves.
          Show clearly how you work out your answer.
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Speed of microwaves................................................ m/s
(2)
(Total 4 marks)
 Q5.          (a)     Some scientists think that there is a link between using a mobile phone and some types of illness. Other scientists disagree. They say that the evidence is limited and unreliable.
(i)      Suggest what scientists could do to show a link between using a mobile phone and illness.
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(1)

(ii)     How could scientists improve the reliability of the evidence?
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(1)

(iii)     Complete the following passage by drawing a ring around the word in the box that is correct.
         There has been little or no experimental research into the health of children who use mobile phones.

This is partly because of the	economic
environmental
ethical	 
issues involved in using	

         children in scientific research.
(1)

(b)     Before being sold, new mobile phones must be tested and given a SAR value.
The SAR value is a measure of the energy absorbed by the head while a mobile phone is being used.
          The table gives the SAR value for three mobile phones made by different companies.
To be sold in the UK, a mobile phone must have a SAR value lower than 2.0 W/kg.
 
Mobile phone	SAR value in W/kg	
J	0.18	
K	0.86	
L	1.40	

(i)      All companies use the same test to measure a SAR value.
         Why is using the same test important?
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(1)

(ii)     Would the companies that make the mobile phones, J, K and L, be correct to claim that these three phones are totally safe to use?
         Answer yes or no. ..............................
         Give a reason for your answer.
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(1)

(c)     Devices designed to protect a mobile phone user from microwave radiation are now available.
          Why is it important that these devices are tested by scientists who are not working for the company that makes the devices?
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(1)
(Total 6 marks)
 Q6.          After a person is injured a doctor will sometimes ask for a photograph to be taken of the patient’s bone structure, e.g. in the case of a suspected broken arm.
(i)      Which type of electromagnetic radiation would be used to take the photograph?
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(1)

(ii)      Describe the properties of this radiation which enable it to be used to photograph bone structure.
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(2)
(Total 3 marks)
 EM spectrum-Mark scheme

M1.         (a)      (i)     microwaves
1

(ii)     can pass through the ionosphere
accept travels in a straight line
accept atmosphere for ionosphere
do not accept air for ionosphere
1

(b)     any two from:
•        analogue is continuously varying
do not accept analogue has many values
•        digital has only discrete values
accept digital is on or off
accept digital is 1 or 0
accept digital is binary
•        digital is less prone to interference (than analogue)
accept digital is easier to restore
•        digital can be processed more easily (than analogue) by a computer
2

(c)     higher the frequency, further the wave travels (into the atmosphere before reflection)
1

(d)     15 000
allow 1 mark for correct transformation and substitution
ie  
an answer of 15 000 000 only gains 1 mark
allow both marks for an answer of 15 MHz (unit must be changed)
an answer of 15 gains no credit
2
[7]
 
M2.         (a)     (i)      to compare mobile phone usage between the two groups
1

(ii)     enough data to indicate relationships
or
reduce effect of anomalous data
1

(b)     (i)      ethical
1
(ii)     research may be biased (in favour of companies)
1
negative effects on health may not get published
accept negative effects on health may be played down
1

(iii)     it allows people to easily identify lower risk phones
1
and this allows people to make a more informed choice
accept and this allows a comparison to be made
1
[7]
 M3.          (a)     gamma rays above x-rays
for 1 mark
(b)     upper radio wave boundary correct (10-1m) (± 1mm)
for 1 mark
(c)     visible radiation/light
•    within the middle third of a wavelength band
•    in the correct wavelength range (10-6 – 10-7m)
each for 1 mark

(d)     ultraviolet between *visible radiation and X-rays
for 1 mark

(e)     microwaves above *radio waves and below *infra red
(*not necessarily immediately)
for 1 mark
(f)      between 108Hz + 107Hz and nearer to 108Hz than to 107Hz
gains 1 mark
[7]

 

M4.          (i)      absorbed by water / water heated
1
          hot water heats (rest of) food / idea of particle vibration
1
(ii)      300 000 000 / 3 × 108
correct answer with no working = 2
allow 1 mark for s = f x w or correct working i.e., 10000 (000000) × 0.03
N.B. correct answer from incorrectly
recalled relationship / substitution = 0
2
[4]
 
M5.          (a)     (i)      compare (the health of) mobile phone users with non-mobile
phone users
must be an implied comparison between users and non-users
any idea of doing an experiment negates the mark
1

(ii)     increase the sample size
accept use more people
accept have a large sample size
repeat the research / test is neutral
1

(iii)     ethical
1

(b)     (i)      so the phones can be compared (fairly)
a fair test is insufficient
accept different tests (may) give different results
do not accept to make the results reliable, unless qualified
eg all variables are controlled
do not accept bias unless qualified
1

(ii)     yes all are below the legal limit / 2 (W/kg)
         or no and any one from:
•        even absorbing a small amount of energy may be harmful
accept microwaves for energy
accept emits energy absorbed by head / other parts of body
•        no proof that small amounts of energy are not harmful
accept because the SAR value is not 0 (W/kg)
1

(c)     any one from:
•        to get an independent opinion
•        company scientists may be biased
accept company scientists may manipulate results
1
[6]
 M6.          (i)      X-rays or gamma rays
for 1 mark
1

(ii)      passes through flesh;
stopped by bone/absorbed
for 1 mark each
2
[3]