The effects depend on the type of radiation and the size of the dose.

The idea

The risk of harm from electromagnetic radiation depends on two main factors: the type of radiation and the size of the dose. Different types cause different effects. For example, ultraviolet waves are absorbed by the skin, causing premature ageing and skin cancer. X-rays and gamma rays are ionising and can penetrate deep into the body to cause gene mutations and cancer. The size of the dose determines the probability of these harmful effects occurring. Radiation dose is a measure of the risk of harm resulting from an exposure of the body to radiation. Students do not need to recall the unit of radiation dose (sieverts), but should be able to interpret data given in sieverts (Sv) or millisieverts (mSv).

What earns the marks

• State that the effect of radiation depends on both the type of radiation and the size of the dose.
• Define radiation dose as a measure of the risk of harm resulting from an exposure of the body to radiation.
• Identify that ultraviolet radiation is absorbed by the skin, leading to premature ageing or skin cancer.
• Explain that X-rays and gamma rays are ionising and can cause gene mutations or cancer.

Common mistakes and how to put them right

• Confusing the type of radiation with the size of the dose.

  Put it right by treating them as two distinct factors that both influence the risk of harm.

• Assuming ultraviolet is highly penetrating ionising radiation.

  Put it right by noting it is primarily absorbed by the skin.

• Treating dose as just the physical amount of radiation energy absorbed.

  Put it right by defining it specifically as a measure of the risk of harm.

Exam tips

• When discussing risk, always mention both the type of radiation and the size of the dose to secure full marks.
• You will be given the units (Sv or mSv) if needed, but you must understand that dose measures the risk of harm.