Radio waves are used mainly for communication. This is because they have long wavelengths (over 10m) which s very useful. Long-wave radio (wavelengths of 1-10km) can be transmitted from London (for example) to half way around the globe. This is because long wavelengths are the best at diffracting, so they can bend around the earth and also arounds opticals such as hills and tunnels.
Radio waves used for broadcasting have mush shorter wavelengths (10cm-10m), these do not bend well so you have to be in direct sight of the transmitter, the is why T.V ariels are positioned on top of houses.
NOTE: as well as long-wave radio signals, short-wave and medium-wave also exist. Short wave radio signals (10m-100m) can also be received long distance from the transmitter because they are reflected from the ionosphere (an electrically charged layer in the Earth's upper atmosphere). Medium-wave signals can also reflect from the ionosphere (but this depends on the atmospheric conditions and the time of day)
Microwaves; cooking and satellite transmissions
Microwaves have wavelengths of around 1cm-10cm, they are used for satellite communication and cooking.
Satellite communication needs to use wavelengths of microwaves which can easily pass through the Earths atmosphere without bing absorbed. For a satellite T.V (for example) to work, the signal from a transmitter is transmitted into space where it is picked up by the satellite receiver did that is orbiting thousands of kilometre above Earth. The satellite transmits the signal back to Earth in a different direction where it is received by a satellite dish on the ground. Mobile phone calls also travel as microwaves from your phone to the nearest transmitter.
Microwaves in ovens have a different wavelength to those used in communication. These microwaves penetrate a few centimetres into the food before being absorbed by water molecules in the food.
Infrared: heaters and night vision equipment
Infrared radiation is also known as heat radiation. Infrared radiation is given out anything and everything, and the hotter the object, the more IR radiation is given out. Examples of infrared radiation in everyday phenomena include electrical heaters and grills. Electrical heaters radiate infrared to keep us warm and grills radio infrared to cook food.
Furthermore, the infrared radiation that objects give out can be picked up/detected during nighttime (or pitch black) by night-vision equipment. the equipment turns the IR that has been radiated into an electrical signal which is displayed on a screen as a picture, meaning things that otherwise would go amiss (e.g. a criminal hiding) to be seen.
Visible light: optical fibres and photography
Visible light can also be used in communication using optical fibres which carry data over long distances as pulses of light.
Optical fibres work by bouncing waves off the sides of a very narrow core. The beam of light enters the fibre at a certain angle as one end and is reflected again and again (known as 'total internal reflection' until it emerges at the other end...
Optical fibres are often used for telephone and broadband internet cables. They are also used in hospitals to see inside the body without having to operate.
Visible light is also used for photography. Cameras use a lens to focus visible light onto a light-sensitive film or electronic sensor (the lens aperture controls how much light enters the camera). The shutter speed determine how long the film or sensor is exposed to the light. by varying the aperture and shutter speed a photographer can capture as much/little light as they want
Ultraviolet: fluorescent lamps
Florescent colours look so bright because it is where ultraviolet radiation (UV) is absorbed and visible light is emitted.
This basically means that fluorescent lights use UV radiation to emit visible light. They are safe to use as nearly all the UV radiation is absorbed by a phosphor coating on the inside of the glass (which emits visible light instead). This is more energy-efficient than filament light bulbs.
X-rays: observing the internal structure of objects and materials and medical applications
To produce an X-ray image, X-ray radiation is directed through your body (or an object you wish to X-ray) onto a detector plate (which starts off white). X-rays can easily pass through mediums such as flesh but not through dense mediums such as bone. The brighter bits (e.g. bones) are where fewer X-rays get through - this is a negative image.
Gamma rays: sterilising food and medical equipment
Medical equipment is sterilised by gamma rays as they kill ass the microbes. This is more effective than boiling equipment as this could potentially cause damage.
Food can be sterilised the same was as medical equipment (by killing the microbes). Is is perfectly safe to eat afterwards, as in like its not radioactive etc.
Thank you so much for this! :)
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