Dangers of High-Energy EM Waves

Types of High-Energy EM Waves

High-energy electromagnetic (EM) waves have shorter wavelengths and higher frequencies, which means they carry more energy. The main types of high-energy EM waves relevant at GCSE level are:

• Ultraviolet (UV) radiation: Just beyond visible violet light, UV has higher energy and is emitted by the Sun.
• X-rays: Produced by X-ray machines and certain radioactive materials, X-rays have enough energy to pass through soft tissues but are absorbed by denser materials like bones.
• Gamma rays: Emitted by radioactive substances and nuclear reactions, gamma rays have the shortest wavelength and highest energy in the EM spectrum.

Health Risks

Because of their high energy, these EM waves can cause damage to living cells and tissues, leading to various health risks:

Skin Damage and Burns from UV Radiation

Ultraviolet radiation from the Sun can damage the skin. Prolonged exposure causes sunburn, which is an inflammatory reaction to skin cell damage. UV radiation can also cause premature skin ageing and increase the risk of skin cancer by damaging the DNA in skin cells.

UV radiation is divided into UVA, UVB, and UVC. UVC is mostly absorbed by the atmosphere, specifically the ozone layer, so UVA and UVB reach the Earth’s surface and affect skin health.

Cell Damage and Cancer Risk

X-rays and gamma rays are types of ionising radiation, meaning they have enough energy to ionise atoms and molecules inside cells. This ionisation can cause mutations in DNA, potentially leading to uncontrolled cell growth and cancer.

Repeated or high exposure to these waves increases the risk of cancers such as skin cancer (from UV) or internal cancers (from X-rays and gamma rays).

Radiation Sickness from High Doses

Very high doses of X-rays or gamma rays can cause radiation sickness, which includes symptoms like nausea, vomiting, hair loss, and damage to internal organs. This occurs because the radiation kills many healthy cells rapidly.

For example, people working with radioactive materials or undergoing repeated medical X-rays must be careful to avoid excessive exposure.

For instance, if a person receives an X-ray dose of 0.02 millisieverts (mSv) and the safe annual limit is 1 mSv for the public, then the number of such X-rays they could safely have in a year is:

$\text{Number of X-rays} = \frac{1}{0.02} = 50$

This means up to 50 X-rays of this dose could be taken in a year without exceeding the public exposure limit.

Protection Measures

To reduce the risks from high-energy EM waves, several protection methods are used depending on the type of radiation:

Use of Sunscreen and Protective Clothing

Sunscreen contains chemicals that absorb or reflect UV radiation, preventing it from reaching the skin. Wearing hats, sunglasses, and long-sleeved clothing also reduces skin exposure to UV rays.

Limiting time spent in direct sunlight, especially during peak hours (10 am to 4 pm), helps reduce UV damage.

Limiting Exposure Time

For X-rays and gamma rays, exposure time is kept as short as possible. Medical X-rays are only used when necessary, and technicians use techniques to minimise patient exposure.

Lead Shielding for X-rays and Gamma Rays

Lead is a dense metal that absorbs X-rays and gamma rays effectively. Lead aprons and shields are used in hospitals and laboratories to protect parts of the body not being examined or to protect workers from scattered radiation.

Increasing distance from radiation sources also reduces exposure, as the intensity of radiation decreases with distance according to the inverse square law.