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Electromagnetic Waves
- Gamma rays and x-rays
- X-rays pass through soft tissue but are absorbed by bone
- X-rays produce radiographs
- Gamma radiation is electromagnetic radiation from radioactive substances
- Gamma rays can be
used to kill harmful
bacteria in food, sterilise
surgical equipment and to
kill cancer cells
- Gamma rays can be
used to kill harmful
bacteria in food, sterilise
surgical equipment and to
kill cancer cells
- Gamma radiation is electromagnetic radiation from radioactive substances
- X-rays produce radiographs
- X-rays pass through soft tissue but are absorbed by bone
- Visible light and ultraviolet radiation
- Light from the Sun and light bulbs is called white light,
because it has all colours of the visible spectrum on it
- Ultraviolet (UV) radiation makes some chemicals emit light
- UV radiation is harmful to the human eye and can cause blindness
- UV radiation comes from the Sun, and too much of it can cause skin cancer
- UV radiation comes from the Sun, and too much of it can cause skin cancer
- UV radiation is harmful to the human eye and can cause blindness
- Ultraviolet (UV) radiation makes some chemicals emit light
- Light from the Sun and light bulbs is called white light,
because it has all colours of the visible spectrum on it
- Infra-red waves, microwaves and radio waves
- All objects emit infra-red radiation
- The hotter an object is the more radiation it emits
- Infra-red radiation is absorbed by the skin, which kills skin cells as they heat up
- Infra-red devices include heaters and remote controls
- Microwaves are shorter than radio waves in
wavelength, even though they come before
radio waves in the electromagnetic spectrum.
This is why they are called microwaves
- We use microwaves for
communication and heating food in
microwave ovens
- Radio waves are longer in wavelength
than microwaves – but appear after
microwaves in the electromagnetic
spectrum because they have a lower
frequency
- We use radio
waves to carry
radio, TV and mobile
phone signals
- Radio waves are emitted from an aerial
- Analogue and digital signals
- Analogue and digital signals
- Radio waves are emitted from an aerial
- We use radio
waves to carry
radio, TV and mobile
phone signals
- Radio waves are longer in wavelength
than microwaves – but appear after
microwaves in the electromagnetic
spectrum because they have a lower
frequency
- We use microwaves for
communication and heating food in
microwave ovens
- Microwaves are shorter than radio waves in
wavelength, even though they come before
radio waves in the electromagnetic spectrum.
This is why they are called microwaves
- Infra-red devices include heaters and remote controls
- Infra-red radiation is absorbed by the skin, which kills skin cells as they heat up
- The hotter an object is the more radiation it emits
- All objects emit infra-red radiation
- The electromagnetic spectrum
- The wavelength of a wave is the distance
from one wave peak to the next wave peak
along the waves
- The frequency is the number of
complete waves passing a point
per second
- We measure frequency in the
unit of hertz (Hz) when:
- - 1 Hz = 1 complete wave per second
- - 1 Hz = 1 complete wave per second
- - 1 kilohertz (kHz) = 1000 Hz
- - 1 megahertz (MHz) =
1,000,000 Hz
- - 1 megahertz (MHz) =
1,000,000 Hz
- - 1 kilohertz (kHz) = 1000 Hz
- - 1 Hz = 1 complete wave per second
- - 1 Hz = 1 complete wave per second
- We measure frequency in the
unit of hertz (Hz) when:
- The speed of a wave is worked out by using:
wave speed (m/s) = frequency (Hz) x
wavelength (m)
- The frequency is the number of
complete waves passing a point
per second
- Alternatively, the
frequency can be worked
out by using:
- frequency = wave speed (in m/s)
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wavelength (in metres)
- frequency = wave speed (in m/s)
________________________________
wavelength (in metres)
- The wavelength of a wave is the distance
from one wave peak to the next wave peak
along the waves
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