P13 Electromagnetic waves:

Radio waves

Radio waves are used to carry radio, tv and mobile signals. You can also use radio waves instead of cables to connect to a computer to other devises.

The wavelength of visible light (what humans can view) ranges from

Just under 400nm to about 700nm

Infrared radiation

All objects emit infrared radiation, the hotter an object is the more infrared radiation it emits, infrared radiation is absorbed by your skin, it can damage, burn or kill skin cells because it hears up the cell.

Radio wavelengths

the radio and microwaves spectrum is divided into bands of different wavelength ranges. The sorter the wavelengths of waves, the more information they can carry, the sorter their range, the less they spread out.

Energy and frequency

the sorter the wavelength of the wave, the higher frequency. The energy of the waves increases as frequency increases.

Electromagnetic waves

these are electrical and magnetical disturbances that can be used to transfer energy from a source to an absorber. These do not transfer matter, the energy they transfer depends on the wave length of waves, this is why waves of different wavelengths have different effects.

X rays

these are usually used to detect internal cracks in metal objects. This is possible because more dance a substance is, the more x ray it absorbed from a beam passing through it. X rays are also used in medicine to detect a broken limb.

The electromagnetic spectrum

(in order of decreasing wavelength and increasing frequency and energy) radio waves, microwaves, infrared radiation, visible light, ultraviolet waves, x rays and gamma waves.

Ultraviolet waves

ultraviolet waves are between violet light and x rays (in the electromagnetic spectrum). Some chemicals emit light as a result of absorbing ultraviolet waves. These waves are harmful to our eyes and can make us blind. UV wavelengths are smaller than visible light wavelengths, they also carry more energy than visible light waves. These waves are harmful to our skin. Your sun cream blocks UV waves and prevents them for reaching your skin.

Wave length (m)

wave speed (m/s) / frequency (Hz)

Frequency (Hz)

wave speed (m/s)/ wavelength (m)

X ray process

when the x ray tube is switched on x rays from the tube pass through Park patients body. X-rays pass through the soft tissue, but there accepted by the bones, the parts of the film or the detector that the x ray reach become darker than other parts. So, the bones appear Lighter than the surrounding tissue, the radio shows a negative image of the bones. A hole of a cavity in a tooth showed up as a dark area in a bright image of the teeth. In organ that consists of soft tissue can be filled with a substance called constant medium that absorbs x rays easily. This allows the initial surface of the organ spacing on the radiography. Let's place between the tube and the patient stops x rays from reaching other parts of the body the x-rays reaching the patients pass through the gap between the plates. Let is used because it is a good observer of x rays. A Flat panel detects a small screen that contains a charged coupled device. The centre of this converts x rays to light. The light rays then create electronic signals in the senses that were sent to the computer which displays digital x ray image.

Light

Light from the sun is called white light, because it has all the coulers of the visible spectrum in to. The wavelength increases across the spectrum as you go from violet to red.

Infrared devices

Optical fibres in communications systems usually use infrared radiation instead of visible light. This is because inferred radiation is absorbed less than visible light in class fibres. Remote controls transmit signals carried by infrared radiation, when you press a button on a remote it sends out a sequence of infrared pulses. Infrared scanners are used in medicine to detect infrared emitted from the body, this means the tissues is unhealthy.

The speed of electromagnetic waves

all electromagnetic waves travel at a speed of 3x10 to the power of 8 (m/s)(300 million m/s) through space or a vacuole.

Using radio waves in a microphone

an oscillator supplies carrier waves to the transmitter in the form of an alternating current. The audio signal is supplied to the transmitter where it is used to moderate carrier waves. The modulated Cartier waves from the transmitter are supplied to the transmitter aerial. The varying alternative current supplied to the Arial causes it to emit radio waves that carry the audio signal. When the radio waves are absorbed by a reserved areal, they induce an alternating current in the receiver aerial, causes oscillations in the receiver. The frequency of the oscillations is the same as the frequency of the radio waves. The receiver circuit separates the audio signal from the carrier waves. The audio signal is then supplied to a speaker, which sends out sound waves similar to the sound waves received by the mice phone in the radio station.

X ray therapy

doctors used x rays to kill cancerous tumours in the body. Thick plated between the x ray tube and body stops x rays from reaching healthy body tissues. A gap between the plates allow x rays through to reach the tumour. X rays for therapy are shorter in wavelength than x rays used for imaging. The x rays used for therapy carry much more energy than x rays used for imaging. Low energy x rays are suitable for imaging because they are absorbed by bones and teeth, but pass through tissue and sales, for example cracked bones. Low energy x rays do not carry enough energy to destroy cancerous tumours.

Wave speed (m/s)

frequency (Hz) x wavelength (m)

Using gamma rays

hammer rays are used to kill harmful bacteria, exposing food to gamma rays kills off disease carrying organisms. Gamma rays also prevent infection from spreading in hospitals, by exposing surgical instruments in sealed plastic wrappers to gamma rays. Gamma rays also kill cancer, gamma rays are used in therapy to destroy cancerous tumours. The narrow beam of gamma rays from a radioactive source is directed at the tumour. The beam is aimed at it from different directions to kill the tumour but not the surrounding tissue.

Communication purposes microwaves are used for

microwaves are used for phone and tv links. This is because microwaves can travel between satellites in space and the ground, they spread out less than radio waves, so the signal is, much stronger. Radio waves are also used from tv broadcasting because they can carry more info than radio waves. Radio waves can be used for local radio stations because their range is limited to the surrounding area.

Microwaves

microwaves have a short wavelength than radio waves. Microwaves are used for communications (Tv because they can pass through the atmosphere and reach satellites above earth, they also carry mobile phone signals). In addition, microwaves are used to heat food.

Optical fingers in comparison to radio and microwaves

optical fibres carry much more information as light has a much shorter wavelength that radio waves, so they can carry more pulse waves. Optical fivers are more secure because the signals stay in the finer.

Optical fibre communications

optical fivers are very thing glass fibres, they are used to transmit signals carried by light of infrared radiation. The light rays can't escape from the finer. When they reach the surface of the fibre, they are reflected back into the fibre.

X rays and gamma rays

these both travel straight into substances and can pass through then if the substances are not too dense and think. These both have similar properties x rays are produced when electrons of other partials moving at a high speed are stopped. Gamma rates are produced by radioactive substances when unstable nuclei release energy. Gamma rays have shorter wavelengths than x rays so they can penetrate substances more than x rays.

Are microwaves and radio waves safe?

they can be hazardous because they penetrate people bodies and can heat internal parts of the body.

More about signals and carrier waves

when you speak, you produce sound waves of different frequencies, so you fairy the amplitude and the frequency of the sound waves you produce. In a radio station, a microphone produces an alternating current called an audio signal when sound waves reach it.

Radio communications

when you use a phone, radio waves carry signal between your mobile phone and the nearest mobile phones mast. The waves used to carry any type of signals are carrier waves. They could be any sort of waves; the type of wave depends on the amount of information is in the signal and the distance the signal has to travel.

Safety matters

x rays and gamma rays passing through substances can knock electrons out of atoms in the substance, the atoms become charged because they lose electrons, this process is ionisation, so x rays and gamma rays are example of ionising radiation. If ionisation happens to a living organism it can damage or kill the cells. For this reason, exposed to too many x rays or gamma rays it is dangerous and can cause cancer.

Radiation dose

x rays, gamma rays and the radiation from radioactive substances all ionise substances they pass through. There are three types of radiation from radioactive substances, gamma radiation, alpha and beta radiation. All of these ionising radiations are dangerous. The radiation dose received by a person is a measure of the damage done to their body by ionising radiation, the radiation dose depends on the type of radiation used, how long the body is exposed to it, the energy per second absorbed by the body from the radiation. Radiation dose is measured in sieverts(Sv), or millisievers (mSV). Hight doses kill cells, low dosage cause gene mutation and cancerous growths.