Electromagnetic waves

Question 1

What are electromagnetic radiations and how do they travel?

Answer 1

Electromagnetic radiations are electric and magnetic disturbances, they travel as waves and move energy from place to place.

Question 2

Give one similarity shared by all electromagnetic waves and two differences.

Answer 2

All electromagnetic waves travel through space at the same speed, but they have different wavelengths and frequencies.

Question 3

What are all the electromagnetic waves collectively known as?

Answer 3

The electromagnetic spectrum.

Question 4

Describe the wavelength and frequency of gamma rays with regard to other waves in the electromagnetic spectrum.

Answer 4

Gamma rays have the shortest wavelength and highest frequency.

Question 5

Describe the wavelength and frequency of radio waves with regard to other waves in the electromagnetic spectrum.

Answer 5

Radio waves have the longest wavelength and lowest frequency.

Question 6

What is the relationship between the frequency of a wave and the amount of energy it transfers?

Answer 6

The higher the frequency of an electromagnetic wave the more energy it transfers.

Question 7

At what speed do all electromagnetic waves travel through space?

Answer 7

300 million m/s

Question 8

What equation links wave speed, frequency and wavelength?

Answer 8

v = f x lambda
Where:
v is the wave speed = 300 000 000 m/s
f is the frequency in hertz, Hz
Lambda is the wavelength in metres, m

Question 9

What is visible light?
How does wavelength and colour vary across the spectrum?
What do we see a mixture of all the colours as?

Give one use of visible light.

Answer 9

Visible light is the part of the electromagnetic spectrum that is detected by our eyes, we see the different wavelengths within it as different colours.
Wavelength increases across the spectrum from violet to red.
White light
Photography

Question 10

Give one application of Infrared radiation.

Answer 10

Remote controls for devices such as Tv’s and radios.

Question 11

How are microwaves used in communications?

Answer 11

Microwave transmitters produce wavelengths that are able to pass through the atmosphere, they are used to send signals to and from satellites and within mobile phone networks.

Question 12

How are radio waves used in communications?

Answer 12

Radio waves transmit radio and TV programs and carry mobile phone signals.

Question 13

What affect can microwave radiation and radio waves have on the body?

Answer 13

Microwave radiation and radio waves penetrate your skin and are absorbed by body tissue, this can heat internal organs and may damage them.

Question 14

What affect can infrared radiation have on the body?

Answer 14

Infrared radiation is absorbed by the skin: too much will burn your skin.

Question 15

What happens when an alternating current is supplied to an aerial?

Answer 15

The aerial emits radio waves with the same frequency as the alternating voltage. When the waves are received they produce an alternating current in the aerial with the same frequency as the radiation received.

Question 16

What is the radio and microwave spectrum split up into?

What are these used for?

Answer 16

The spectrums are divided into different bands

The different bands are used for different communication purposes.

Question 17

What is the relationship between the wavelength of the waves and the amount of information they carry?

How does a wave with a short range behave?

Answer 17

The shorter the wavelengths of the waves the more information they carry.

The shorter a waves range, the less they spread out.

Question 18

What part of the body and in which age group especially do scientists believe mobile phones may affect?

Answer 18

The brain and especially in children

Question 19

What are optical fibres and for what are they used?

How do signals travel down the fibre?

Answer 19

Optical fibres are very thin glass fibres , we use them to transmit signals carried by visible light or infrared radiation.
By repeated total internal reflection

Question 20

Why are optical fibres useful in communications?

Answer 20

They are useful in communications because they carry much more information and are more secure than radio wave and microwave transmissions.

Question 21

What is the Doppler effect?

Give an example of the doppler effect demonstrated with sound waves.

Answer 21

If a wave source is moving relative to an observer, the wavelength and frequency of the waves detected by the observer shift from the original produced by the source.

An ambulance siren will sound different depending on whether it is moving away from you; pitch is lower. Or moving toward you pitch is higher.

Question 22

What happens to the frequency and wavelength, when a source moves away from the observer?

Answer 22

The observed wavelength increases and the frequency decreases.

Question 23

What happens to the frequency and wavelength, when a source moves towards the observer?

Answer 23

The observed wavelength decreases and the frequency increases.

Question 24

What is a galaxy?

What is red-shift?

Answer 24

A large collection of stars.
Red-shift is where light observed from distant galaxies has been shifted to the red end of the spectrum, this means that the frequency has decreased and the wavelength increased.

Question 25

What does a blue-shift indicate?

How are we able to see these effects?

Answer 25

A blue-shift would indicate that a galaxy is moving towards us.
We are able to see these effects by observing dark lines in the spectra from galaxies.

Question 26

The further away the galaxy, the bigger the red-shift, what does this suggest about distant galaxies?

Answer 26

This suggests that distant galaxies are moving away from us, and the most distant galaxies are moving the fastest.

This is true of galaxies no matter which direction you look.

Question 27

What evidence is there to suggest that the universe is expanding?

Answer 27

Red-shift

All the distant galaxies are moving away from each other

Question 28

What does the fact that the universe is constantly expanding outwards suggest about how the universe was created and where it started from?
What is this theory called?

Answer 28

It suggests that it started with a massive explosion at a very small initial point, this is known as the Big Bang Theory.

Question 29

What is comic microwave background radiation?

What is the only theory to explain the existence of CMBR?

Answer 29

This is the radiation produced by the big bang.

The Big Bang Theory

Question 30

If the universe began with a Big Bang then what would have been produced?
What would this have become as the universe expanded?

Answer 30

High energy gamma radiation, as the universe expanded this would have become lower-energy radiation.