Electromagnetic Waves (AQA GCSE Physics Combined Science): Revision Notes
Dangers and uses
Energy and electromagnetic waves
The energy carried by an electromagnetic wave depends on its frequency and wavelength. Waves with higher frequencies (shorter wavelengths) carry more energy. This means they are more dangerous to living things.
The relationship between frequency and energy is direct: as frequency increases, energy increases proportionally. This is why high-frequency waves like gamma rays are so dangerous compared to low-frequency radio waves.
The electromagnetic spectrum ranges from low-energy radio waves to high-energy gamma rays. The higher the frequency, the more harmful the wave can be to your body.
Dangers of electromagnetic waves
Different types of electromagnetic waves can harm your body in different ways depending on their energy levels:
High-frequency waves (most dangerous)
Gamma rays and X-rays are the most dangerous types of electromagnetic radiation because they carry enough energy to damage the very building blocks of life.
Gamma rays and X-rays
- Can damage DNA in your body cells
- This damage can cause mutations that lead to cancer
- Can kill cells completely
- Gamma rays come from radioactive materials
Ultraviolet (UV) rays are found in everyday sunlight and cause more health problems than people realise.
Ultraviolet (UV) rays
- Found in sunlight
- Damage skin cells and cause sunburn
- Long-term exposure can cause skin cancer
- Can also damage your eyes and cause eye problems
Medium-frequency waves
Infrared radiation
- Carries heat energy
- Too much can cause skin burns
- Your body naturally gives off infrared radiation
Microwaves
- Heat up water molecules
- Can heat water inside your body
- This heating can damage or kill body cells
Low-frequency waves (least dangerous)
Radio waves
- Carry the least energy
- Generally safe for humans
- Used for communication without major health risks
Uses of electromagnetic waves
Each type of wave has important practical applications that benefit society:
Gamma rays
- Sterilise medical equipment and food
- Treat cancer patients
- Detect cancer in body scans
X-rays
- Take pictures inside your body (medical X-rays)
- Security scanners at airports
- Detect fake banknotes (they glow under UV light)
Medical Application: Bone Fracture Detection
When you break a bone, X-rays pass through soft tissue but are absorbed by dense bone material. This creates a clear image showing:
- Dark areas = soft tissue (X-rays pass through)
- Light/white areas = bones (X-rays blocked)
- Fracture lines appear as dark lines through the bone
Ultraviolet light
- Sterilise water
- Security markings on banknotes
- Fluorescent lamps
Visible light
- Helps us see everything around us
- Photography
- Lights up streets and buildings
Infrared radiation
- Cooking food (grills and toasters)
- Thermal imaging cameras
- Remote controls for TVs
- Short-range communication between devices
Microwaves
- Cooking food (microwave ovens)
- Mobile phone signals
- Communication with satellites
- Security systems and burglar alarms
Radio waves
- Broadcasting radio and TV programmes
- Mobile phone networks
- Satellite communication
- Ship and aircraft communication
Radiation dose
Radiation dose is a critical safety measurement that tells us how much harmful radiation your body absorbs and the potential health risks involved.
Radiation dose measures how much harmful radiation your body absorbs. It tells us the risk of harm to your health.
The units used are:
- Sieverts (Sv) - the main unit
- Millisieverts (mSv) - smaller unit (1000 mSv = 1 Sv)
Safe levels
- We naturally get less than 1 mSv per year from background radiation
- This is considered safe
- A dose of 7 Sv is very dangerous and could cause death
Background radiation comes from natural sources like cosmic rays from space, radioactive elements in soil and rocks, and even from foods like bananas which contain small amounts of radioactive potassium.
The effect of radiation on your body depends on:
- The type of radiation
- How much radiation you receive
- How long you are exposed to it
Key Points to Remember:
- Higher frequency electromagnetic waves carry more energy and are more dangerous
- Gamma rays and X-rays can cause cancer by damaging DNA
- UV light causes sunburn and skin cancer from too much sun exposure
- Each type of wave has useful applications in medicine, communication, and technology
- Radiation dose is measured in sieverts (Sv) or millisieverts (mSv) to show health risks