Dangers of EM Waves

This lesson covers the hazards associated with different parts of the electromagnetic spectrum, the difference between ionising and non-ionising radiation, and the safety precautions used to reduce risk, as required by the Edexcel GCSE Combined Science specification (1SC0).

---

Ionising vs Non-Ionising Radiation

EM waves can be classified as ionising or non-ionising based on their energy and their ability to remove electrons from atoms (ionisation).

Category	EM Waves	Energy	Effect on Atoms
Non-ionising	Radio waves, microwaves, infrared, visible light	Lower	Cannot remove electrons from atoms; mainly cause heating
Ionising	Ultraviolet (higher energy UV), X-rays, gamma rays	Higher	Can remove electrons from atoms; can damage DNA and cause mutations

What Is Ionisation?

Ionisation is the process where radiation has enough energy to knock an electron out of an atom, turning it into an ion. This can:

• Damage or destroy cells.
• Cause mutations in DNA.
• Lead to cancer if the mutations affect cell division.

Exam Tip: The key dividing line is between visible light and ultraviolet. UV, X-rays and gamma rays are classed as ionising radiation. Make sure you can state this clearly.

---

Dangers of Each Type of EM Wave

Radio Waves

Danger	Detail
Risk level	Very low
Effect	No significant known health effects at normal exposure levels
Notes	Radio waves have very low energy and pass through the body without causing damage

---

Microwaves

Danger	Detail
Risk level	Low to moderate (at high intensity)
Effect	Heating of body tissue, particularly water-containing tissue
Specific risk	Internal heating of organs — the body may not detect the heat quickly enough to prevent damage

Safety precautions:

• Microwave ovens have metal mesh screens in the door that reflect microwaves back inside.
• The door seal prevents leakage.
• Ovens have a safety interlock that switches off the microwaves when the door is opened.

---

Infrared (IR)

Danger	Detail
Risk level	Low to moderate
Effect	Skin burns and thermal damage to tissue
Specific risk	Prolonged exposure can cause burns; high-intensity IR can damage eyes

Safety precautions:

• Wear protective clothing and use heat shields when working near very hot objects.
• Avoid prolonged exposure to intense IR sources.

---

Visible Light

Danger	Detail
Risk level	Low (unless very intense)
Effect	Eye damage from very bright sources (e.g. looking directly at the Sun, laser beams)
Specific risk	Damage to the retina, temporary or permanent blindness

Safety precautions:

• Never look directly at the Sun or at a laser beam.
• Wear laser safety goggles in laboratories.
• Appropriate warning labels on laser equipment.

---

Ultraviolet (UV)

Danger	Detail
Risk level	Moderate to high
Effect	Sunburn, premature skin ageing, skin cancer, eye damage (cataracts)
Specific risk	UV is ionising — it can damage DNA in skin cells, leading to mutations and cancer (especially melanoma)

Safety precautions:

• Wear sunscreen (high SPF) and reapply regularly.
• Wear UV-blocking sunglasses to protect eyes.
• Wear protective clothing (hats, long sleeves).
• Limit time in direct sunlight, especially between 11 am and 3 pm.
• Use UV-protective screens in workplaces where UV lamps are used.

Exam Tip: UV is the most commonly examined EM wave in terms of dangers. Make sure you can explain that UV is ionising, damages DNA, and causes skin cancer. Always link the danger to the mechanism.

---

X-rays

Danger	Detail
Risk level	High
Effect	Cell damage, mutations, cancer
Specific risk	X-rays are highly ionising and penetrating — they can damage deep tissue and organs

Safety precautions:

• Radiographers stand behind lead-lined screens or leave the room during exposure.
• Patients wear lead aprons to shield parts of the body not being imaged.
• X-ray exposure is kept to a minimum — only taken when medically necessary (ALARA principle: As Low As Reasonably Achievable).
• Radiographers wear dosimeters (film badges) to monitor their cumulative exposure.

---

Gamma Rays

Danger	Detail
Risk level	Very high
Effect	Cell destruction, mutations, cancer, radiation sickness (at high doses)
Specific risk	Gamma rays are the most penetrating and most ionising EM waves; they can pass through the body and damage internal organs

Safety precautions:

• Sources are handled with long tongs or robotic arms — never by hand.
• Stored in lead-lined containers.
• Exposure time is kept as short as possible.
• Workers maintain maximum distance from the source.
• Thick lead or concrete shielding is used in treatment rooms and nuclear facilities.
• Workers wear dosimeters to monitor exposure.

Exam Tip: For ionising radiation safety, remember the three principles: minimise time of exposure, maximise distance from the source, and use appropriate shielding.

---

The ALARA Principle

ALARA stands for As Low As Reasonably Achievable. This principle is applied to all uses of ionising radiation:

• Only use ionising radiation when the benefit outweighs the risk.
• Keep exposure time to a minimum.
• Keep distance from the source as great as possible.
• Use appropriate shielding (lead aprons, lead screens, concrete walls).

---

Comparing the Effects of EM Waves on the Body

EM Wave	Main Effect on Body	Ionising?
Radio waves	No significant effect	No
Microwaves	Heating of tissue (especially internal)	No
Infrared	Burns, skin damage	No
Visible light	Eye damage (intense sources)	No
Ultraviolet	Sunburn, skin cancer, eye damage	Yes (higher energy UV)
X-rays	Cell damage, mutations, cancer	Yes
Gamma rays	Cell destruction, mutations, cancer, radiation sickness	Yes

---

Worked Example

Explain why radiographers leave the room when taking an X-ray image of a patient.

• X-rays are ionising radiation.
• Prolonged or repeated exposure can damage DNA in cells, leading to mutations and potentially cancer.
• The patient only receives a brief, targeted dose, but the radiographer would be exposed many times each day.
• By leaving the room (or standing behind lead shielding), the radiographer minimises their cumulative exposure, following the ALARA principle.