Describe the harmful effects on people of excessive exposure to…

The idea

Excessive exposure harms people in ways that depend on how each band interacts with tissue, not simply on frequency. Microwaves are absorbed and heat body cells internally, because they penetrate to tissue beneath the skin. Infrared is absorbed at the surface, so overexposure causes skin burns. Ultraviolet is absorbed strongly by surface cells and the eye, damaging them and raising the risk of skin cancer and eye conditions such as cataracts. X-rays and gamma rays carry enough energy per photon to ionise atoms, so they can mutate DNA or damage cells, which may lead to cancer. Learn each band with its own effect and the tissue it affects.

What earns the marks

• Links microwaves to internal heating of body cells rather than to surface burns.
• Links infrared to skin burns caused by surface absorption.
• Links ultraviolet to damage of surface cells and eyes, including skin cancer and eye conditions.
• Links x-rays and gamma rays to mutation or damage to cells in the body.
• Distinguishes the tissue affected by each band instead of assuming deeper penetration always accompanies higher frequency.

Common mistakes and how to put them right

• Assumes that higher frequency always means deeper penetration.

  Put it right by noting that microwaves heat internal cells while infrared and ultraviolet act mainly at the surface.

• Treats all electromagnetic bands as causing identical harm.

  Put it right: Match each band to its stated effect.

• Attributes skin burns to ultraviolet and cell mutation to infrared.

  Put it right: Swap these so infrared gives burns and ultraviolet damages surface cells and eyes.

• Ignores the eye when describing ultraviolet.

  Put it right: Include eye conditions alongside skin cancer.

Exam tips

• Read the stem to see which band is named, then select the effect that belongs to that band alone.
• Use the tissue named in the option (internal cells, skin surface, eyes, DNA) as a quick check on whether the pairing is correct.
• Eliminate options that swap effects between bands before choosing your answer.