Rainbows

Waves

The white light spectrum

1. White light is a mixture of different colours of light.

2. Newton used a glass prism to separate the colours.

3. He identified 7 different colours.

4. Initials ROYGBIV

Waves

The white light spectrum

Violet is refracted more than red

The prism refracts the light

Light Wavelengths

Waves

The electromagnetic spectrum

Waves

Electromagnetic waves

1. Light is a transverse wave

2. It is one part of a much bigger family

3. This family is called

electromagnetic waves

Waves

Electromagnetic waves – common features

1. Transverse

2. Can travel through empty space

3. Speed in empty space

300 000000m/s (186 000 miles per second – not hour)

4. Can be reflected, refracted, diffracted.

Waves

Electromagnetic waves – differences

Each part is made of waves with different

1. frequencies and

2. wavelengths

Waves

Electromagnetic waves – parts

1. Radio/tv

2. Microwaves

3. Infra-red

4. Visible light

5. Ultraviolet

6. X-rays

7. Gamma - rays

Long waves

Low frequency

Short waves

High frequency

Waves

Electromagnetic waves – parts

1. Radio/tv

2. Microwaves

3. Infra-red

4. Visible light

5. Ultraviolet

6. X-rays

7. Gamma - rays

Waves

Electromagnetic waves – parts

Waves

Radio-TV waves

• Used to transmit radio and TV programmes

Waves

Radio-TV waves

• Long waves reflected by the ionosphere and can travel long distances

ionosphere

Waves

Microwave radiation - 1

• Used for transmitting information to satellites

Waves

Microwave radiation - 2

• Mobile phones transmit and receive microwaves

Waves

Microwave radiation - 3

1. Microwaves are absorbed by water making it hot

2. they can penetrate and cook food with a water content.

Action of microwaves

Waves

Infra red radiation - 1

• Can be detected by the skin as heat.

• Emitted by all ‘hot’ objects

Waves

Infra red radiation - 2

1. Used for cooking in grills and toasters

2. Used for heating in radiant type heaters

Waves

Infra red radiation - 3

• TV remote controls emit infra red

Waves

Infra red radiation - 4

• Passive infra red detector used for alarm systems

Waves

Visible light

• Used for seeing – the eyes detect light

Waves

Visible light

• Cameras detect light

Waves

Visible light

• Air, water, glass etc let light pass through them. They are transparent.

Waves

Ultra violet radiation - 1

• Fluorescent tube light produce uv inside the tube

Waves

Ultra violet radiation - 2

• Sun beds contain uv lamps

Waves

Ultra violet radiation - 3

• UV is used in security coding – special inks glow under UV.

Waves

X-radiation (rays) - 1

1. X-rays can travel through skin, muscle or flesh.

2. X-rays cannot travel through bone or metal

3. They are used to produce shadow pictures of bones and metal

X ray cat pin

Waves

X-radiation (rays) - 2

Waves

Gamma radiation (rays) -1

• Gamma rays can kill harmful bacteria in food.

Waves

Gamma radiation (rays) - 2

• Gammas are used to sterilise surgical equipment

Waves

Gamma radiation (rays) - 3• Gamma rays are used in medicine to kill

cancer cells

Stars emit em waves

Stars emit all types of em waves

1. we see the visible

2. Feel the IR

3. May be damaged by the UV

4. Astronomers ‘look’ at all the parts

Waves

The effect on living cells of microwaves

1. Absorbed by the water in cells

2. The cells can be damaged or killed by the heat

Waves

The effect on living cells of infra red

1. Absorbed by skin

2. Felt as heat

3. Can cause burns

Waves

The effect on living cells of ultra violet

1. Can pass through skin to deeper tissues.

2. Absorbed more by darker skin

3. High doses can kill normal cells

Waves

The effect on living cells of X –rays and gamma rays

• Can pass through soft tissues

• Some is absorbed by the cells

• High doses can kill normal cells

• Low doses can cause normal cells to mutate and become cancerous

Waves

Ionising radiation

• Gamma and X radiation are ionising and must be treated with caution.

• They can be both useful and dangerous.