P13 - Electromagnetic Waves✔️

Question 1

Why do electromagnetic waves have different effects?

Answer 1

Electromagnetic waves do not transfer matter - the energy they transfer depends on the wavelength of the waves this is why waves of different wavelengths have different effects

Question 2

What speed do electromagnetic waves travel at?

Answer 2

300 million m/s through space or in a vacuum

Question 3

Equation for wave speed?

Answer 3

Wave speed = frequency x wavelength

Question 4

Electromagnetic waves in order of increasing frequency and decreasing wavelength?

Answer 4

Radiowaves - microwaves - infrared radiation - visible light - unltraviolet waves - x rays and gamma rays

Question 5

Why is light from ordinary lamps and from the sun called white light?

Answer 5

Because it contains all the colours of the visible spectrum in it

Question 6

Features of infrared radiation?

Answer 6

-hotter an object more infrared radiation is emmited

-infrared radiation is absorbed by your skin , it can damage,burn or kill skin cells

Question 7

3 uses of infared radiation?

Answer 7

-infrared scanners - used in medicine to detect unhealthy tissues

-see people and animials in the dark

-heat up obects quickly - electric heaters emit infared which warms rooms quick

Question 8

3 features of microwaves?

Answer 8

-Shorter wavelength then radio waves

-used for communications for example satellite TV because they pass through the atmosphere and reach satelites above earth

-heating up food

Question 9

Why are microwaves used to heat up food?

Answer 9

Microwave ovens heat food faster because microwaves can penetrate into food and are absorbed by the water molecules in the food

Question 10

Fequency and fetaures of radiowaves?

Answer 10

frequencies range from about 300,000 Hz to 3000 million Hz and are used to carry tv and mobile phone signals

Question 11

Why can radio and microwaves be hazardous?

Answer 11

They penetrate peoples bodies and can heat the internal parts of the body causing damage

Question 12

Define carrier waves?

Answer 12

Waves used to carry any type of signal they could be radiowaves,microwavess or visible light - they do this by varying their amplitude

Question 13

A shorter wavelength results in …?

Answer 13

-The wave carrying more information

-shorter the waves range (increasing absorption by the atmosphere)

-the less the waves spread out

Question 14

3 uses of microwaves?

Answer 14

-satelite phone

-tv links

-satelite TV broadcasting

Question 15

Why are microwaves used for satelite TV braodcasting?

Answer 15

Microwaves can travel between satelites in space and the ground and they spread out less than radio waves so the signal doesn’t weaken as much

Question 16

Uses of radiowaves less than about 1 metre?

Answer 16

-TV braodcasting from TV masts - because they can carry more infromation than longer radiowaves

Question 17

Uses of radiowaves about 1 to 100 metres?

Answer 17

-used by local radiostations and for emergency services because the range is limited to the area round the trasmitter

Question 18

Uses of radiowaves greater than 100 metre?

Answer 18

Used by national and international radio stations because they have much longer range than shorter wavelength radio waves

Question 19

How can mobile phones radiowaves be dangrous?

Answer 19

If the phone is very close to the your head , some scientists think the radiation might affect the brain especialy in children because they have thinner skulls then adults

Question 20

What are optical fibres?

Answer 20

Very thin transparent fibres that are used to transmit communication signals by light and infarred radiation

Question 21

Benefits of optical wires?

Answer 21

-carry much more information as light has a much shorter wavelength than radio waves and so can carry more impulses of waves

-optical fibres are more secure because the signals stay in the fibre

Question 22

Issues with sunbeds and UV light?

Answer 22

Ultraviolet waves are harmful to your skin - and to much UV from the sun or from sunbeds can cause sunburn and skin cancer

Question 23

Why is lead used to stop x-rays and gamma rays?

Answer 23

Because x-rays and gamma rays both travel straight into substances and can pass through them if the substance is not dense and thick enough so lead is often used

Question 24

Similar properties between x-rays and gamma rays?

Answer 24

-are at the short-wavelength end of the electromagnetic spectrum

-carry more energy per second than longer-wavelength electromagnetic waves

Question 25

Different properties between x-rays and gamma rays?

Answer 25

-x-rays are produced when electrons or other particles moving at high speeds are stopped - x-ray tubes are used to produce x-rays -gamma rays are produced by radioactive substances when unstable nuclei release enegry -gamma rays have shorter wavlengths than x-rays so they can penetrate more than x-rays can

Question 26

2 uses of x-rays?

Answer 26

-used to detect internal cracks in metal objects - more dense a substance is the more x-rays it abbsorbs from an x-ray beam passing through it -medecine ot reate images of broken limbs

Question 27

2 uses of gamma rays?

Answer 27

-exposing food to gamma rays to kill bacteria and disease carrying organisms -disinfecting and steralising surgical equipment to kill any bactiera

Question 28

Explain how and why gamma rays are used for killing cancerous cells?

Answer 28

Use gamma rays to destroy cancerous tumours - narrow beam of gamma ray from a radioactive source is directed at the tumour and is aimed in a way as to not kill the healthy surrounding tissue

Question 29

Define ionisation?

Answer 29

The process in which 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

Question 30

Why is ionising radiation dangrous?

Answer 30

ionisation to living cells can damage or kill the cell - with low doses causing gene mutation and cancerous growth

Question 31

Exaplain in 3 steps how x-rays are used to identify damages to the bone ?

Answer 31

1)x-ray tub is switched on and x-rays pass from tube through the part of the patients body being investigated 2)x-rays pass through soft tissue and cracks in bone but are absorbed by bones so the parts of the film or detector that the x-ray reach become darker then the other parts so the bone apears lighter the surrounding tissue 3)flat-panel detector containing a CCD converts the x-rays to light - light rays then create electronic signals which are are sent to a computer to display a digital x-ray image

Question 32

How can an organ or soft tissue be seen on the radiograph?

Answer 32

Soft tissue can be filled with a substance called a contrast medium that absorbs x-rays easily which enables the internal surface in the organ to be seen on the radiograph - patient also given a barium meal before the x-ray because it is a good absorber of x-rays

Question 33

Method the stop x-rays reaching other parts of the body?

Answer 33

Lead plate are used between the tube and the patient

Question 34

What is a flat-panel detector and how does it help display the x-ray as a digital image?

Answer 34

Is a small screen that contains a charge-coupled device (CCD) - the sensors in the CCD convert x-rays to light - the light rays then create electronic signals in the sensors that are sent to a computer whch displays a digital x-ray image

Question 35

2 types of ioning radiation in the form of particles?

Answer 35

-beta -alpha

Question 36

2 types of ioning radiation in the form of waves?

Answer 36

-x-rays -gamma rays

Question 37

3 factors that effect radiation dose?

Answer 37

-type of radiation used -how long the body is exposed to it -the energy per second absorbed by the body from the radiation

Question 38

Why are low-energy x-rays suitable for imaging?

Answer 38

-absorbed by bones and teeth but pass through soft tissue and gaps such as cracks in the bone -do not carry enough energy to destroy cancerous tumours