Radiation Final

8/3/2019 Radiation Final

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MADE BY: HAMZAH IMRAN, YASIR SABIR, ABDUL-AHAD [X-B]



1. INTRODUCTION…………………………....................................2

2. THE ELECTROMAGNETIC SPECTRUM………………………..3

3. RADIO WAVES…………………………………………………………..4

4. MICRO WAVES…………………………………………………………..5

5. INFRARED WAVES…………………………………………………….6

6. VISIBLE LIGHT…………………………………..………………………7

7. ULTRAVIOLET [UV] WAVES………..…………………………….8

8. X-RAY WAVES……………………………………………………….....9

9. GAMMA RAYS………………………………………………………….10

10. SOURCES………………………………………………………………11



Radiation = directional energy transfer by rapid oscillations of energy fields

treated as discrete particles

…and/or as rays in ‘geometric optics’

Eectromagnetic Radiation characterized by: Wavelength (λ), frequency (ν)

λ =c/ν

Where c = speed of light (3 x 108 m s-1 )

Wavelength is the distance between any next equal position on the wave, e.g. wave

crests or where I=0

Units: µm, nm, m

Frequency is the number of waves passing a point per unit time

Units: s-1, i.e. Hz



The electromagnetic spectrum isthe range of all possible

frequencies of electromagnetic

radiation. The "electromagnetic

spectrum" of an object is the

characteristic distribution of

electromagnetic radiation emitted

or absorbed by that particular

object.

The electromagnetic spectrumextends from low frequencies usedfor modern radio communication togamma radiation at the short-wavelength (high-frequency) end,thereby covering wavelengths from

thousands of kilometers down to afraction of the size of an atom. It isfor this reason that theelectromagnetic spectrum is highlystudied for spectroscopic purposesto characterize matter. The limit for long wavelength is the size of theuniverse itself, while it is thought

that the short wavelength limit is inthe vicinity of the Planck length,although in principle the spectrumis infinite and continuous.



Radio

waves are made by

various types oftransmitter , depending

on the wavelength. They

are also given off by

stars, sparks and

lightning, which is why

you hear interference on

your radio in a thunderstorm. Radio waves are the lowest frequencies in the electromagnetic spectrum, and are

used mainly for communications.

Radio waves are divided into:- Long Wave, around 1~2 km in

wavelength. The radio station "Atlantic252" broadcasts here.

Medium Wave, around 100m inwavelength, used by BBC Radio 5 andother "AM" stations.

VHF, which stands for "Very HighFrequency" and has wavelengths of around 2m. This is where you find stereo"FM" radio stations, such as BBC Radio1and Further up the VHF band arecivilian aircraft and taxis.

UHF stands for "Ultra High Frequency",and has wavelengths of less than ametre. It's used for Police radiocommunications, televisiontransmissions and military aircraft radios- although military communications arenow mostly digital and encrypted.



Microwaves are basicallyextremely high frequency radiowaves, and are made by varioustypes of transmitter . In a mobile phone, they're

made by a transmitter chip and anantenna, in a microwave oven they're made by a "magnetron".

Their wavelength is usually a couple of centimetres. Stars also give off microwaves.

Microwaves cause water and fat molecules to vibrate, which makes the substanceshot. So we can use microwaves to cook many types of

food. Mobile phones use microwaves, as they can be

generated by a small antenna, which means that the phonedoesn't need to be very big. The drawback is that, beingsmall, they can't put out much power, and they also need aline of sight to the transmitter. This means that mobile phone

companies need to have many transmitter towers if they're going to attract customers. Microwaves are also used by fixed traffic speed cameras, and for radar , which is

used by aircraft, ships and weather forcasters. The most common type of radar works by sending out bursts of microwaves, detecting

the "echoes" coming back from the objects they hit, and using the time it takes for theechoes to come back to work out how far away the object is.

Prolonged exposure to microwaves is known to cause "cataracts" in your eyes, whichis a clouding of the lens, preventing you from seeing clearly (if at all!) So don't make a

habit of pressing your face against the microwave oven door to see if your food'sready!

Recent research indicates that microwaves from mobile phones can affect parts of your brain - after all, you're holding the transmitter right by your head. Other researchis inconclusive, although there is a feeling that you're more vulnerable if you're youngand your brain is still growing.So the advice is to keep calls short.



Infra red waves are just belowvisible red light in the electromagneticspectrum ("Infra" means "below"). You probably think of Infra-red

waves as heat, because they're given off by hot objects, and you can feel them as

warmth on your skin. Infra Red waves are also given off by stars, lamps,

flames and anything else that's warm - including you. The detector on this security light picks up the Infra red

radiation from your body. Infra-red waves are called "IR" for short. They are used for many tasks, for example, remote

controls for TVs and video recorders, and physiotherapistsuse heat lamps to help heal sports injuries. IR is also used

for short-range communications, for example between mobile phones, or for the Dolby

Screentalk headset system used in some cinemas. Because every object gives off IR waves, we can use them to "see in the dark". Night

sights for weapons sometimes use a sensitive IR detector. one of the most common modern uses for IR is in the field of security. "Passive Infra-

Red" (PIR) detectors are used in burglar alarm systems, and to control the securitylighting that many people have fitted outside their houses. These detect the Infra-Redemitted by people and animals.

You've probably seen TV programmes in which police helicopters track criminals at

night, using "thermal imaging" cameras which can see in the dark. These camerasuse Infra-Red waves instead of "ordinary" light, which is why people look bright inthese pictures. Similar cameras are also used by fire crews and other rescueworkers, to find people trapped in rubble.

Weather forecasters use satellite pictures to see what's heading our way. Some of the images they use are taken using IR cameras, because they show cloud and rainpatterns more clearly.



Our eyes can detect only a tiny part of the electromagnetic spectrum,called visible light.. Light waves are given off by

anything that's hot enough to glow. This is how light bulbs work -

electric current heats the lamp filamentto around 3,000

degrees, and itglows white-hot.

The surface of the Sun is around 5,600 degrees, and it gives off a great deal of light.

White light is actually made up of a whole range of colours,mixed together. We can see this if we pass white

light through a glass prism - the violet light

is bent ("refracted") more than the red, because it has a shorter wavelength - and we see a rainbow of colours. [This is called'dispersion', and allows us to work out what stars are made of by looking at the mixture of wavelengths in the light].

We use light to see things! As the Sun sends so much light towards our planet, we'veevolved to make use of those particular wavelengths in order to sense our environment.

Light waves can also be made using a laser. This

works differently to a light bulb, and produces"coherent" light.

Lasers are used in Compact Disc & DVD players,where the light is reflected from the tiny pits in thedisc, and the pattern is detected and translated intosound or data.

Lasers are also used in laser printers, and in aircraftweapon aiming systems



Ultra-Violet light is made by specia

lamps, for example, on sun beds. It is givenoff by the Sun in large quantities. We call it

"UV" for short.

Uses for UV light include getting asun tan, detecting forged bank notes inshops, and hardening some types of dentalfilling.

You also see UV lamps in clubs,where they make your clothes glow. Thishappens because substances in washing powder "fluoresce" when UV light strikesthem - they absorb the UV and then re-radiate the energy at a longer wavelength. Thelamps are sometimes called "blacklights" because we can't see the UV coming fromthem.

When you mark your posessions with a security marker pen, the ink is invisible unlessyou shine a UV lamp at it.

Ultraviolet rays can be used to kill microbes. Hospitals use UV lamps to sterilisesurgical equipment and the air in operating theatres. Food and drug companies alsouse UV lamps to sterilise their products.

Suitable doses of Ultraviolet rays cause the body toproduce vitamin D, and this is used by doctors to treat vitamin Ddeficiency and some skin disorders. The cheaper sunglasses tend not to protect you against UV,

and this can be really dangerous. When you wear sunglasses thepupils of your eye get bigger, because less light reaches them.

This means that if your sunglasses don't block UV, you'llactually get more ultra-violet light in your eyes than if you didn't

wear them, although you won't notice at the time. So before you buy sunglasses, checkthat they offer UV protection!.

Large doses of UV cause sunburn and even skin cancer . Fortunately, the ozone layer inthe Earth's atmosphere screens us from most of the UV given off by the Sun. Think of asun tan as a radiation burn!



X-rays are very high frequency waves,and carry a lot of energy. They will passthrough most substances, and this makes themuseful in medicine and industry to see insidethings. X-rays are given off by stars, and

strongly by some types of nebula. An X-ray machine works by firing a beam of electrons at a "target". If we fire the

electrons with enough energy, X-rays will be produced. X-rays are used by doctors to see inside people. The machines are managed by a

trained x-ray technician. They pass easily through soft tissues, but not so easilythrough bones. We send a beam of X-Rays through the patient and onto a piece of film, which goes dark where X-Rays hit it. This leaves white patches on the film wherethe bones were in the way.

Sometimes a doctor will give a patient a "Barium Meal", which is a drink of BariumSulphate. This will absorb X-rays, and so the patient's intestines will show up clearly

on a X-Ray image. X-Rays are also used in airport security

checks, to see inside your luggage. They are alsoused by astronomers - many objects in theuniverse emit X-rays, which we can detect usingsuitable radio telescopes. Lower energy X-Rays don't pass through

tissues as easily, and can be used to scan soft

areas such as the brain X-Rays can cause cell damage and cancers. This is why Radiographers in hospitals stand behind

a shield when they X-ray their patients. Although thedose is not enough to put the patient at risk, theytake many images each day and could quickly buildup a dangerous dose themselves.



Gamma rays are given off by stars, and

by some radioactive substances. They are extremely high frequencywaves, and carry a large amount of energy. They pass through most materials, andare quite difficult to stop - you need lead or concrete in order to block them out. Because Gamma rays can kill living cells,they are used to kill cancer cells without

having to resort to difficult surgery. This is called "Radiotherapy", and works because cancer cells can't repair themselveslike healthy cells can when damaged by gamma rays.Getting the dose right is very important!

There's also targeted radiotherapy, where a radioactivesubstance is used to kill cancer cells - but it's a substancethat'll be taken up by a specific part of the body , so therest of the body only gets a low dose. An example wouldbe using radioactive iodine to treat cancer in the thyroid

gland. Radioactivity is particularly damaging to rapidly dividing

cells, such as cancer cells. This also explains why damage is done by radiotherapy toother rapidly dividing cells in the body such as the stomach lining (hence nausea), hair follicles (hair tends to fall out), and a growing foetus (not because of mutations, but simplymajor damage to the baby's rapidly dividing cells).

Doctors can put slightly radioactive substances into a patient's body, then scan thepatient to detect the gamma rays and build up a picture of what's going on inside the

patient. This is very useful because they can see the body processes actually working,rather than just looking at still pictures.

In industry, radioactive "tracer" substances can be put into pipes and machinery, then wecan detect where the substances go. This is basically the same use as in medicine

Gamma rays cause cell damage and can cause a variety of cancers. They cause mutations in growing tissues, so unborn babies are especially vulnerable.



SOURCES:

http://www.darvill.clara.net/emag/emagradio.htm

http://science.hq.nasa.gov/kids/imagers/ems/radio.html

http://www.darvill.clara.net/emag/emagmicro.htm

http://science.hq.nasa.gov/kids/imagers/ems/micro.html

http://www.darvill.clara.net/emag/emaginfra.htm

http://science.hq.nasa.gov/kids/imagers/ems/infra.html

http://www.darvill.clara.net/emag/emagvis.htm

http://science.hq.nasa.gov/kids/imagers/ems/vis.html

http://www.darvill.clara.net/emag/emaguv.htm

http://science.hq.nasa.gov/kids/imagers/ems/uv.html

http://www.darvill.clara.net/emag/emagxray.htm http://science.hq.nasa.gov/kids/imagers/ems/xrays.html

http://www.darvill.clara.net/emag/emaggamma.htm

http://science.hq.nasa.gov/kids/imagers/ems/gamma.html





















http://www.darvill.clara.net/emag/emagxray.htm


http://science.hq.nasa.gov/kids/imagers/ems/xrays.html




















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Radiation Final

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