Electromagnetic Waves

What is the pattern of the wavelength and frequency in EM waves?

• As you move from gamma rays to radio waves, the wavelengths increase and the frequencies decrease

• wave energy increases with frequency

• wave energy decreases with wavelength

• gamma rays have the shortest wavelength and the highest frequency

• radio waves have the longest wavelength and the lowest frequency

What’s the order of the EM waves in order of the highest frequency to the lowest?

gamma. X-ray, ultraviolet, visible light, infrared, microwave and radiowaves

Gamma Rays

• uses- medical imaging and therapy, sterilisation

• risks- they are extremely penetrating and damaging to living tissues and cells

• they carry most energy

• they can be used to destroy bacteria and tumours

X- rays

• uses- medical and industrial imaging, used for security purposes to detect weapons in airports

• risks- they are high ionising so they can damage body cells

• x-rays penetrate soft materials like body tissue so bones which are more dense can absorb x-rays so they can be used to build a shaded image of bones and body tissue

Ultraviolet Light

• uses- detect fake bank notes

• risks- exposure to too much UV light can cause skin burns and skin cancer

• In lamps, UV excites (gives energy to) atoms which then can release visible light

Infrared Radiation

• uses- TV controls, security purposes such as intruder alarms by detecting body heat

• risks- can cause serious skin burns if emitted from high intensity osurces

Microwaves

• uses- microwaves to cook food

• risks- exposure to microwaves could have a harmful effect as humans are largely made up of water

• microwaves travel in straight lines through the atmosphere which makes them good for transmitting signals

Radio Waves

• uses- radio and TV communications

• risks- at high intensities, radio waves can cause internal heating of living tissue with potentially harmful effects

• they have long wavelengths, they ccan be transmitted around buildings without interference

What’s refraction?

• a wave’s speed can change when moving from one medium to another

• if the wave crosses to the new medium at an angle, the change in the wave’s speed will cause the direction of the wave’s motion to change and the wave will appear to bend called refraction

What’s reflection?

• Reflection happens when a wave hits a flat surface (plane) and bounces off

What’s absorption?

• when waves ,eet some materials, the energy is absorbed by the material

• e.g when light falls on a balck surface, most of energy is absorbed

What’s transmission?

• When waves carry on travelling through a new material

• often leading to refraction