Electromagnetic waves

Question 1

Do higher or lower frequency waves have more energy?

Answer 1

Higher frequency waves

Question 2

Do longer or shorter wavelength waves have more more energy?

Answer 2

Shorter wavelength

Question 3

What is the critical angle?

Answer 3

The angle at which total internal reflection occurs and no refraction takes place

Question 4

What is the angle of incidence?

Answer 4

The angle at which light enters a object

Question 5

What conditions are needed for refraction?

Answer 5

The angle of incidence must be greater than the critical angle

Question 6

What pathway will light take if the angle of incidence is equal to the critical angle?

Answer 6

The light will be refracted along the boundary

Question 7

What conditions are needed for TIR (Total internal reflection?

Answer 7

The angle of incidence must be greater than the critical angle

Question 8

What is meant by the term monochromatic?

Answer 8

Made up of only ONE colour of light, with one single frequency

Question 9

What is meant by the term phase difference?

Answer 9

The difference between one wave and another when you compare the cycles of of each wave

Question 10

What is meant by the term divergence?

Answer 10

How much light waves spread out as they travel

Question 11

Why do laser produce an intense beam of light?

Answer 11

They carry a large amount of energy and have a low divergence so they concentrate light in a small area.

Question 12

Why do lasers produce a coherent beam of light?

Answer 12

They produce a monochromatic light with a single frequency which has waves that are all in phase

Question 13

True or false;

Laser produce waves that are ‘In phase’

Answer 13

True

Question 14

In regards to the pathway of light when entering different mediums, what is the normal line?

Answer 14

The pathway that light would take if it didn’t enter a medium of a difference density and refract

Question 15

What is morse code an example of?

Answer 15

A digital code

Question 16

True or false;
Digital codes are a method of representing information from only two different states.
Give an example to support your answer

Answer 16

True

Eg. dots/dashes, on/off, up/down, 1/0 etc.

Question 17

What are the two states of a digital wave?

Answer 17

Peaks and troughs, they can a different values

Question 18

Why do digital waves suffer from less interference?

Answer 18

Because they have only two values, unlike analogue signals which have continuous values, and therefore interference on the waves can be easily removed because it is still clear what the states and values of the digital waves actually are.

Question 19

Why are infrared waves only suitable for short distance communication?

Answer 19

Because they are easily obstructed, so wouldn’t be suitable for long range communication

Question 20

What is multiplexing?

Answer 20

Multiplexing is when communications from several sources are transferred through the same cable, they are then filtered out again at the other end of the cable

Question 21

What is demultiplexing?

Answer 21

The process which separates (filters out) individual signals which have been transmitted over a single data stream, alongside signals from several other sources.
It is the opposite, and reverse process, of multiplexing?

Question 22

How does the curvature of the earth impede a signal? How do we combat this?

Answer 22

Because waves travel in straight lines and therefore will not follow the curvature of the earth and therefore we must use reflection (using either the ionosphere or satellites) to direct waves around the earth

Question 23

Why do microwaves only require small receivers but radio waves require larger receivers?

Answer 23

As microwaves have a shorter wavelength, they only require a small receiver however, as radio waves have a much larger wavelength, they need a larger receiver

Question 24

Why is total internal reflection used in fibre optics?

Answer 24

To transmit signals around curves in the fibre optic cables

Question 25

Why are fibre optic connections much faster than standard connections?

Answer 25

Because they transmit huge amounts of information, using multiplexing, at the speed of light.

Question 26

Which type of wave penetrates the ionosphere? Why?

Answer 26

Microwaves, because they have a higher frequency and short wavelength so they contain more energy and therefore they aren't affected by a low density gas, such as ionosphere, which they penetrate. Satellites are required to reflect them back towards surface transmitters

Question 27

Which type of wave reflects off the ionosphere? Why?

Answer 27

Radio waves, because they have a lower frequency and long wavelength so they contain less energy and therefore they will refract as the density in the atmosphere changes, eventually they will reflect of the low density ionosphere and travel back towards the surface

Question 28

What process could the effect of the ionosphere be broadly likened to?

Answer 28

Total internal reflection

Question 29

Is the ionosphere dense?

Answer 29

No, it is not very dense

Question 30

What happens to gases in low temperatures?

Answer 30

They begin to sink

Question 31

What happens to the ionosphere in low temperatures? | What effect does this have?

Answer 31

As it is a low density gas, it begins to sink and therefore is closer to the earths surface. This restricts the range of radio waves reflecting off the ionosphere and can create problems when sending radio waves over long distances

Question 32

Give some examples of uses for radio waves?

Answer 32

- Televisions and radios | - Computers, bluetooth and Wi-Fi

Question 33

Give some examples of uses of microwaves?

Answer 33

- Cooking | - Mobile phones

Question 34

Give some examples of uses for inferred waves?

Answer 34

- Cooking - TV remotes (Short range communication) - Automatic lights and burglar alarms (Infrared waves detect heat)

Question 35

Out of radio waves and microwaves, which has the most energy?

Answer 35

Microwaves, because they have a higher frequency and low wavelength.

Question 36

Name a disadvantage to communicating using microwaves?

Answer 36

- They require line of sight communication and are obstructed or scattered by various means. - They do not diffract - Microwaves could interfere with other microwaves working off similar frequencies

Question 37

What are microwaves scattered by?

Answer 37

They are obstructed and scattered by; Objects/ buildings, hills, poor weather and storms, large bodies of water and the curvature of the earth.

Question 38

Which type of electromagnetic wave requires line of sight communication?

Answer 38

Microwaves

Question 39

Name two characteristics of electromagnetic waves?

Answer 39

1) They are all transverse waves | 2) They all travel at the same speed in a vacuum

Question 40

What are the possible health risks associated with microwaves?

Answer 40

There is limited evidence to suggest that microwaves have a heating effect of the brain, this would be particularly detrimental to children who have thinner skulls than adults

Question 41

Name some advantages of wired communication, as oppose to wireless communication?

Answer 41

- Wired communication can make use of multiplexing to send vast amounts of data at rapid speeds. - No interference in the final signal, this can be an issue with wireless communication

Question 42

How do radio waves send signals around the curvature of the earth?

Answer 42

Because they reflect off the ionosphere to travel back to the surface

Question 43

Give some advantages of radio wave communication?

Answer 43

- Reflects off the ionosphere to travel around the curvature of the earth - Will diffract around objects

Question 44

Why can't radio waves transmit large amounts of information?

Answer 44

Because they have a low frequency.

Question 45

Which two types of electromagnetic waves require 'line of sight' communication

Answer 45

Infrared waves and microwaves