Section 3 c) Specification

3.10 understand that light is part of a continuous electromagnetic spectrum which
includes radio, microwave, infrared, visible, ultraviolet, x-ray and gamma
ray radiations and that all these waves travel at the same speed in free
space

Visible light is found in the middle of the electromagnetic spectrum, a range of frequencies of waves:

3.11 identify the order of the electromagnetic spectrum in terms of decreasing
wavelength and increasing frequency, including the colours of the visible
spectrum

In order of increasing frequency and decreasing wavelength, the electromagnetic spectrum is:

Radio Waves

Microwaves

Infrared radiation

Visible light

• Red
• Orange
• Yellow
• Green
• Blue
• Indigo
• Violet

Ultraviolet light

X-rays

Gamma rays

3.12 explain some of the uses of electromagnetic radiations, including:

• radio waves: broadcasting and communications
• microwaves: cooking and satellite transmissions
• infrared: heaters and night vision equipment
• visible light: optical fibres and photography
• ultraviolet: fluorescent lamps
• x-rays: observing the internal structure of objects and materials and medical applications
• gamma rays: sterilising food and medical equipment

Radio waves are used for broadcasting and communications, satellite transmissions, etc.

Microwaves are used for cooking and satellite transmissions

Infrared radiation is used for heaters, cooking (like in toasters) and night vision equipment, short range communications (e.g. tv remotes).

Visible light is used for optical fibres, photography, and everyday screens, lighting, etc.

Ultraviolet light is used for fluorescent lights, tanning beds, disinfecting water, detecting forged bank notes, etc.

X-rays allow us to see inside objects, for example bones inside a body or security screening through suitcases at airports.

Gamma rays are used for killing cancer cells, sterilising food and medical equipment, and detecting cancer.

3.13 understand the detrimental effects of excessive exposure of the human body
to electromagnetic waves, including:

• microwaves: internal heating of body tissue
• infrared: skin burns
• ultraviolet: damage to surface cells and blindness
• gamma rays: cancer, mutation

and describe simple protective measures against the risks.

Even with their many uses, electromagnetic waves have dangerous side effects. The most common hazards are:

Microwaves cause internal heating of body tissues, which is dangerous because it can cause enzymes to denature and badly damage the body. Contact with microwaves can be avoided by ensuring that when they are used, it is in low doses and higher doses are contained (in microwave ovens, they are only emitted when it is switched on and the door is closed)

Infrared radiation can cause burns to the skin, it is felt as heat therefore its hazards are heat related. It can be reduced by shiny silvery surfaces.

Ultraviolet rays, emitted by the sun, kill and cause mutations in skin cells, leading to skin cancer. It can also permanently damage sensitive parts of the eye and cause blindness, as well as sun burn, which is why it is important to wear sun cream, sun glasses, and hats or clothes that cover and protect from the sun.

Gamma rays can kill cancer cells, but in untargeted or incorrect exposure, it can cause cells to mutate and therefore cause cancer. This can be avoided by simply avoiding environments where you could come into contact with gamma rays, but it can be reduced and contained by concrete or lead.