Electromagnetic Waves Flashcards

Question

Cancer treatment

Answer 1

Cancer is a disease in which cells divide in an uncontrolled way because of changes in their DNA. This can form tumours. One method of treating cancer is to direct high energy X-rays or gamma rays at the tumours. This causes so much damage to the cancerous cells that they die. This treatment is called radiotherapy.

Answer 2

It is important that the gamma radiation hits the cancerous cells without hitting too many of the healthy cells. To do this, more than one beam of radiation is used. This means that less of the healthy cells are damaged by the radiation.

Answer 3

Nucleus of atoms following alpha (α) or beta (ß) emission.

Answer 4

Radiotherapy Killing bacteria by irradiation Reduce spoilage of food Kill pathogens (Salmonella and clostridium) Sterilise medical instruments

Answer 5

Exposure can damage cell DNA which can cause cancer.

Answer 6

x rays are absorbed by bone x rays travel through skin

Answer 7

it is partially reflected when it meets a boundary between two different media travels at different speeds through different media

Answer 8

radio waves, microwaves, IR, visible light, UV, X-rays, gamma rays

Answer 9

Radio waves

Answer 10

Dark, matt objects absorb and emit IR radiation at a faster rate than light coloured shiny objects.

Answer 11

Radio waves Microwaves Light Infrared radiation

Answer 12

Medium (1 - 100m) They don’t need a very long range, and they don’t need to carry too much information so a medium wavelength is used.

Answer 13

Long ( more than 100m) These need to have a long range, so longer wavelengths are used

Answer 14

Short ( less than 1m) TV signals carry images, so they carry more information than just the sound used in radio. Therefore they need a shorter wavelength.

Answer 15

Microwaves are used for satellite links because they are capable of getting through the ionosphere

Answer 16

Radio waves are transmitted from radio masts by applying alternating current. These radio waves are detected by an aerial and their frequency causes an alternating potential difference to be induced in the receiver. Radio wave signals are split into bands of different wavelength ranges.

Answer 17

An oscillator supplies carrier waves (which carry the signal) to the transmitter in the form of an alternating current (changes direction all the time) At the radio station, a microphone produces audio waves when sound waves reach it. Audio waves are supplied to the transmitter. The transmitter combines the audio waves and carrier waves = modulated radio waves. The modulated radio waves are supplied to the transmitter aerial. The aerial emits the modulated radio waves that carry the signal. Radio waves are absorbed by the receiver aerial and induces AC (frequency is the same as the radio wave). The audio waves are supplied to a loudspeaker which sends out sound waves.

Answer 18

Satellite TV signals are carried by microwaves. We can detect the signals on the ground because they can pass straight through a layer of ionised gas in our upper atmosphere. This layer of gas, called the ionosphere, reflects longer wavelength, lower frequency radio waves back to earth.

Answer 19

Microwaves carry signals between your mobile phone and the nearest mobile phone mast. The signal is sent using a carrier wave which is modulated (changing the frequency or amplitude) to include the information in your text message. The message is then forwarded to the recipient through the phone network, then to their phone from their closest mobile phone mast.

Answer 20

Mobile phones use similar waves to microwave ovens. For this reason, some scientists believe they can be harmful - especially to children because they have thinner skulls than adults.

Answer 21

Optical fibres use light and IR to transfer information. These waves have a shorter wavelength than radio, so they can carry more information. The signals are contained within thin optical fibres and cannot escape, so optical fibres are more efficient.

Answer 22

They are very secure : the signal stays in the fibre so they cannot be intercepted light and IR waves have a shorter wavelength and higher frequency than radio waves. More pulses are transmitted every second so more information can be sent.

Answer 23

1) two ball bearings are each stuck to one side of a metal plate with solid pieces of candle wax. the other sides of these plates are then faced towards the fame 2) the sides of the plates that are facing towards the flame each have a different surface colour, one is matte black and one is silver. 3) the ball bearing on the matte black plate will fall first as the black surface absorbs more infrared radiation - transferring more energy to the thermal energy store of the wax. this means the wax on the black plate melts before the wax on the silver plate.

Answer 24

1) place an empty Leslie cube on a heat proof mat. 2) boil a kettle and fill the Leslie cube with boiling water. 3) wait for the cube to warm up, then hold a thermometer against each of the four vertical faces of the cube. you should find that all four faces are the same temperature 4) hold an infrared detector a set distance away from one of the cubes vertical faces, and record the amount of IR radiation it detects 5) repeat this measurement for each of the cubes vertical faces. make sure you position the detector at the same distance from the cube each time 6) you should find that you detect more infrared radiation from the black surface that the white one and more from the matt surfaces than the shiny ones 7) as always you should do the experiment more than once to make your results more repeatable

Answer 25

dont move the cube when its full of boiling water, you might biurn your hands be careful when carring a kettle