P1 6 Electromagnetic Waves

Question 0

What does the energy the wave transfers depend on?

Answer 0

Its wavelength

Question 1

What are electromagnetic waves?

Answer 1

Electric and magnetic disturbances that transfer energy from one place to another (can travel through a vacuum)

Question 2

What is the order of the electromagnetic spectrum?

Answer 2

Radio waves
Microwaves
Infrared radiation
Visible light
Ultra violet
X-ray
Gamma rays

Question 3

What speed do all electromagnetic waves travel at?

Answer 3

300 million m/s

Question 4

What is the formula for calculating the speed of a wave?

Answer 4

Speed = frequency x wavelength

Question 5

What happens to the frequency as the wavelength shortens?

Answer 5

It increases

Question 6

How does frequency link with energy?

Answer 6

The higher frequency the more energy.

Question 7

What is a kilohertz and megahertz equal to?

Answer 7

Kilo- 1000

Mega- 1000000

Question 8

What is light from ordinary lamps and the sun known as?

Answer 8

White light

Question 9

Why is it known as white light?

Answer 9

It has all the colours of the visible spectrum

Question 10

Which has a longer wavelength?red or violet?

Answer 10

Red

Question 11

What is done to light in a film camera?

Answer 11

Light is focused by the camera lens onto a light-sensitive film.
The film is then developed to see the objects that have been photographed.

Question 12

What is done to light in a digital camera?

Answer 12

Light is focussed by the lens on to a sensor which has lots of tiny light sensitive cells called pics. These are dots in images.
The image is seen on a small screen at the back of the camera.
When the photograph is taken, it is stored electronically on a memory card.

Question 13

What do all objects emit?

Answer 13

Infra red radiation

Question 14

Infra red radiation is absorbed by the skin. What can it cause?

Answer 14

Damages and kills skin cells because they get heated.

Question 15

State some infra red devices and why they use infra red.

Answer 15

Optical fibres in communications systems: it is absorbed less than light in the glass fibres
Remote control: transmit signals
Infrared scanners: to detect ‘hot spots’
Infrared cameras: to see people and animals in the dark

Question 16

State some microwave devices and why they use microwaves.

Answer 16

Communications: can pass through atmosphere
Mobile phone signals and beam signals: doesnt diffract much
Heating food: agitates water molecules

Question 17

State some radiowave devices and why they use radiowaves.

Answer 17

Connection from computers to devices: have a wide frequency range

Question 18

Give an example of a use for each wave.

Answer 18

Radio - tv signals
Microwaves - heating food
Infrared - remote controls
Visible light - cameras
Ultraviolet - detect forgery, kill pathogens
X-ray - security
Gamma - sterilise, kills cancerous cells

Question 19

The shorter the wavelength of the wave?

Answer 19

The more information they carry
The shorter their range
The less they diffract and spread out

Question 20

What are microwaves used for in communications?

Answer 20

Satellite TV and TV links and broadcasting because they can they can travel between satellites in space and the ground and spread less so signal isn’t weakened as much.

Question 21

What are microwaves less than a metre used for?

Answer 21

Tv broadcasting and masts as they carry more information than longer ones.

Question 22

What are radiowaves from a metre to 100m used for?

Answer 22

Local radio stations and emergency services as the range is limited to the area around its transmitter.

Question 23

What are radio waves more than 100m used for?

Answer 23

National and international radio stations as they have a much longer range.

Question 24

How does a mobile phone signal work?

Answer 24

It sends a radio signal which is picked up by the nearest phone Nast and is sent through the phone network to the other phone. The returning is the signal goes back through the network to the mast neatest to you.

Question 25

What are optical fibres?

Answer 25

Thin glass fibres.

Question 26

What are optical fibres used for?

Answer 26

Transmit signals by light and infrared.

Question 27

How do optical fibres work?

Answer 27

The light cannot escape from the fibre so is reflected back from the surface into the fibre.

Question 28

Why are optical fibre communications better than radio and microwaves?

Answer 28

They carry much more information | They are more secure as all signals stay inside

Question 29

How do radio communications work?

Answer 29

The waves are emitted from an aerial when we apply an alternating voltage. These frequencies are the same. When these waves pass across a receiver aerial they cause a tiny alternating voltage in the aerial. These frequencies are the same. The alternating voltages cause the loudspeaker to send out wves.

Question 30

Explain the Doppler effect.

Answer 30

As the object making the sound moves towards a person, a higher frequency is heard due to the waves being squashed together and creating a shorter wavelength. As it moves away a lower frequency is created as they are further apart and longer wavelength.

Question 31

What does a spectrum of a star consist of?

Answer 31

Dark lines called absorption lines. This is where light is absorbed

Question 32

What does red shift and blue shift tell us?

Answer 32

Read shift means that the lines are moving towards the red end. It means the wave length is stretched and is moving away from us. The faster a galaxy or star is moving the bigger the shift. Vise versa for blue shift.

Question 33

What is the Big Bang theory?

Answer 33

A theory which explains the beginning of the universe.

Question 34

How did the Big Bang start?

Answer 34

From a massive explosion from a very small initial point.

Question 35

What three things were created in the big bang?

Answer 35

Space Time Matter

Question 36

What has been happening ever since the Big Bang?

Answer 36

The universe has been expanding.

Question 37

What other thing is being created by the Big Bang?

Answer 37

Cosmic microwave background radiation

Question 38

What is cosmic microwave background radiation?

Answer 38

A high energy gamma radiation created after the Big Bang. It has been stretched ever since and is now microwaves.