AQA GCSE Physics Foundation (8463), Foundation tier · Waves › Electromagnetic waves
Practise EM waves: production and hazards. 6 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
How electromagnetic waves are produced and absorbed (by changes in atoms and nuclei), and the harm that ultraviolet, X-rays and gamma rays can do to the body. Expect recall questions and 'use the data' questions on radiation dose.
Key facts
EM waves can be produced or absorbed by changes in atoms and nuclei
Gamma rays come from changes in the nucleus
Ultraviolet: premature skin ageing and higher risk of skin cancer
X-rays and gamma rays: ionising; can cause mutation of genes and cancer
Radiation dose (Sv) = a measure of the risk of harm from exposure
1 Sv = 1000 mSv
Notes
Producing and absorbing EM waves
EM waves over a wide range of frequencies can be produced or absorbed by changes inside atoms and their nuclei. For example, when electrons in atoms change energy level, EM waves such as light can be emitted or absorbed.
Gamma rays come from changes in the nucleus of an atom.
Hazards to the body
Ultraviolet, X-rays and gamma rays can have hazardous effects on human body tissue. The effects depend on the type of radiation and the size of the dose.
Ultraviolet can cause skin to age prematurely and increases the risk of skin cancer.
X-rays and gamma rays are ionising radiation. They can cause the mutation of genes and cancer.
Radiation dose
Radiation dose, in sieverts (Sv), is a measure of the risk of harm from the body being exposed to radiation.
1000 millisieverts (mSv) = 1 sievert (Sv). You do not need to remember the unit, but you must be able to use it.
The bigger the dose, the greater the risk. Use given data to compare risks, for example the dose from a medical scan with the yearly dose from background radiation, and to judge whether a benefit is worth the risk.
How to answer each type of question
State the hazards of ultraviolet, X-rays and gamma rays
1 to 4 marksGrade 4
Ultraviolet: skin ageing prematurely and risk of skin cancer.
X-rays and gamma rays: ionising, so mutation of genes and cancer.
Use these exact effects; 'it damages you' is too vague.
Example. (a) Give two harmful effects of ultraviolet radiation on the human body. (b) Explain why X-rays can cause cancer.
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(a) It makes skin age prematurely (1). It increases the risk of skin cancer (1). (b) X-rays are ionising radiation (1), so they can cause mutation of genes, which can lead to cancer (1).
Convert between Sv and mSv
1 to 2 marksGrade 5
Sv to mSv: multiply by 1000.
mSv to Sv: divide by 1000.
Example. A radiographer receives a dose of 0.0035 Sv in one year. Convert this dose into millisieverts.
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0.0035 × 1000 (1) = 3.5 mSv (1)
Don’t lose marks
Describing radiation dose vaguely as 'how much radiation'. It is a measure of the risk of harm from exposure to radiation.
Confusing mSv and Sv: 5 mSv is 0.005 Sv, not 5000 Sv.
Saying gamma rays come from electrons. They come from changes in the nucleus.
In data questions, writing only 'it is more dangerous' without using the numbers.
More tips
Memory tricks
The dangerous three are at the high-frequency end: ultraviolet, X-rays, gamma rays.
Milli means a thousandth: mSv → Sv, divide by 1000; Sv → mSv, multiply by 1000.
Exam technique
In data questions, quote values from the table and make a comparison, e.g. 'the CT dose is 400 times bigger'.
In risk questions, weigh up both sides: the benefit (e.g. a diagnosis) against the risk from the dose.
Name specific effects: 'skin cancer', 'mutation of genes', 'skin ageing prematurely'.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Name the EM waves that harm body tissueUltraviolet, X-rays and gamma rays can have hazardous effects on human body tissue.
Grade 4
State the effects of ultraviolet on skinUltraviolet can make skin age prematurely and increases the risk of skin cancer.
Grade 5
State the effects of X-rays and gamma raysThey are ionising radiation and can cause mutation of genes and cancer.
Grade 5
State where gamma rays come fromGamma rays come from changes in the nucleus of an atom.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Give one harmful effect of ultraviolet radiation on the skin.
It increases the risk of skin cancer (or causes premature ageing of the skin).
What is meant by ionising radiation?
Radiation that can knock electrons out of atoms, forming ions.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Some types of electromagnetic radiation can be hazardous to human body tissue.
(a) Which two types of electromagnetic radiation are ionising? Tick (✓) two boxes.[2]
Gamma rays
Infrared
Microwaves
Visible light
X-rays
(b) Give one harmful effect of ultraviolet radiation on the skin.[1]
(c) Gamma rays are produced by changes in one part of an atom. Which part? Tick (✓) one box.[1]
The electrons
The nucleus
The outer shell
(d) Give one harmful effect of X-rays on body tissue.[1]
Show the answer and mark scheme
(a)Answer: Gamma rays; X-rays
(b)Answer: It increases the risk of skin cancer (or causes premature ageing of the skin).
makes the skin age prematurely / increases the risk of skin cancer
(c)Answer: The nucleus
(d)Answer: They can cause mutation of genes, leading to cancer.
mutation of genes / cancer
Question 2Medium8 marks
A sunbed uses lamps that emit ultraviolet radiation to tan the skin.
(a) Give two risks of using a sunbed.[2]
(b) A leaflet states that 10 minutes on a sunbed gives about the same ultraviolet dose as 1 hour in strong midday sunshine. A person uses the sunbed for 25 minutes, twice a week. Calculate the number of hours of strong midday sunshine that give the same ultraviolet dose as one week of these sunbed sessions.[2]
(c) Some sun creams absorb ultraviolet radiation. Explain how using this type of sun cream reduces the risk of harm.[2]
(d) A radiographer takes many X-ray images each day. The radiographer stands behind a lead screen when the X-ray machine is switched on. Explain why.[2]
Show the answer and mark scheme
(a)Answer: Premature ageing of the skin and an increased risk of skin cancer.
the skin ages prematurely
increased risk of skin cancer
(b)Answer: 5 hours
time on sunbed each week = 2 × 25 = 50 minutes
50 ÷ 10 × 1 = 5 (hours)
(c)Answer: The cream absorbs ultraviolet, so less reaches the skin and the dose is smaller.
less ultraviolet reaches / is absorbed by the skin (cells)
so the dose to the skin is smaller
(d)Answer: The lead absorbs X-rays; without it the radiographer’s dose would build up over many images and increase the risk of cancer.
lead absorbs X-rays, so the radiographer’s dose is reduced
the dose from many X-rays each day would add up, increasing the risk of gene mutation / cancer