P13-Electromagnetic waves

Question 1

What is the order of the electromagnetic spectrum?

Answer 1

Radio waves, microwaves, infrared, visible light, ultraviolet radiation and x rays and gamma radiation.

Question 2

What wavelength can the human eye detect?

Answer 2

Only visible light at a wavelength of 400 to 700.

Question 3

What is the wave speed equation?

Answer 3

Wave speed(m/s) = Frequency(Hz) x wavelength(m)

Question 4

What is white light?

Answer 4

It is light from ordinary lamps and from the sun, it has all the colours of the visible spectrum in it.

Question 5

What is infrared radiation?

Answer 5

All objects emit it and the hotter an object is, the more infrared radiation it emits. It is absorbed by your skin and can damage, burn or kill skin cells as it heats them up.

Question 6

What are 3 devices that use infrared radiation?

Answer 6

Optical fibres in communications, remote control handsets for TV controls and infrared scanners that are used in medicine.

Question 7

What are microwaves?

Answer 7

It has a shorter wavelength than radio waves and people use them for communications in satellites and ovens, as they heat food faster than ordinary ovens.

Question 8

What are radiowaves?

Answer 8

They have frequencies from 300,000 Hz upwards to 3000 million Hz and are used to carry radio, TV and mobile phone signals.

Question 9

What are carrier waves?

Answer 9

They are used to carry any type of signal.

Question 10

What does the frequency of radio waves affect?

Answer 10

How far they can travel, how much they can spread and how much information they can carry.

Question 11

How do carrier waves work?

Answer 11

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’s used to modulate the carrier waves, which are supplied to the aerial, emitting radio waves and carrying an audio signal. When they are absorbed, they induce a current and start the noise. They also do this by varying their amplitude.

Question 12

What are optical fibres?

Answer 12

They are very thin glass fibres used to transmit signals carried by light. This light cannot escape from the fibre and when they reach the surface of the fibre, they are reflected back into the fibre. They are more secure and carry more information than radio and microwaves.

Question 13

What is UV?

Answer 13

It is between violet light and X-rays in the spectrum. They are harmful to human eyes and can also be harmful to your skin.

Question 14

What are X-rays and gamma rays?

Answer 14

They are short wavelength and carry lots of energy. However it is different to gamma rays as X-rays are produced from electrons travelling at high speeds are stopped and gamma rays are produced by radioactive substances when unstable nuclei releases energy. Gamma rays also have a shorter wavelength.

Question 15

How can gamma rays be used?

Answer 15

By killing harmful bacteria in food or surgical instruments and killing cancer cells.

Question 16

How are gamma and X-rays dangerous?

Answer 16

As they are ionising, knocking electrons out of atoms in the substance, giving the substance a charge. This can damage cells.

Question 17

Why are X-rays used?

Answer 17

They are used to make images of internal body parts and to destroy tumours at or near the body surface.

Question 18

How do X-rays work?

Answer 18

They pass through soft tissues but are absorbed by bones, teeth and metal objects. An organ of soft tissue can be filled with a contrast medium that absorbs X-rays. The rays are converted to light through a charge-coupled device, which displays the image.

Question 19

What does the radiation dose depend on?

Answer 19

The type of radiation used, how long the body is exposed to it and the energy per second absorbed by the body from the radiation.

Question 20

What is X-ray therapy?

Answer 20

It is where doctors use it to destroy cancerous tumours in the body through the use of short wavelength X-rays. Therefore they carry more energy than imaging X-rays which do not have the energy to destroy tumours.