Light and Electromagnetic spectrum

Question 1

What is a ray diagram used for?

Answer 1

A way of modelling what happens when light is reflected or refracted

Question 2

What do the rays show in a ray diagram?

Answer 2

The direction the waves are travelling in

Question 3

What is a normal?

Answer 3

Line drawn at right angles to the barrier or mirror

Question 4

What is the incident ray and the reflected ray?

Answer 4

• Incident ray is the ray going towards the mirror or barrier
• Reflected ray is the ray that is reflected back

Question 5

What is the law of reflection?

Answer 5

When the angle of reflection (measured from the normal) is equal to the angle of incidence (this then means that it has been reflected

Question 6

What happens when a wave moves into a different material and what is this called?

Answer 6

It changes direction because they change speeds in different materials - called refraction

Question 7

What is the interface?

Answer 7

Something that separates two different materials or matters - the boundary

Question 8

What happens when light meets the interface at right angles?

Answer 8

It means it has moved along the normal and has no change in direction

Question 9

Where does light travel faster, through air or through glass/water

Answer 9

Air

Question 10

What happens when light passes through water or glass with small angles of incidence?

Answer 10

Most is refracted out but a small amount is reflected

Question 11

What is the angle of refraction?

Answer 11

The angle measured from the normal to the refracted ray

Question 12

What is the relationship between the angle of incidence and the angle of refraction?

Answer 12

As the angle of incidence increases so does the refraction angle

Question 13

What happens after the angle of refraction has increased so much that it is now along the interface at a right angle to the normal and the angle of incidence increases and what is it called?

Answer 13

If the angle of incidence increases any further, then the incidence ray will only reflect not refract anymore - it is called total internal reflection

Question 14

What is the critical angle?

Answer 14

The minimum angle at where total internal reflection occurs

Question 15

How do you investigate refraction?

Answer 15

• Use a ray box with a single slit
• Place glass block on paper and draw outline
• See where light goes after exiting the glass and draw crosses on rays
• Take block away and join crosses and lines before and after it enters the block
• Measure angles of incidence and refraction
• Repeat experiments at different angles

Question 16

What is diffuse reflection?

Answer 16

When a light ray is reflected on a rough surface so the light is scattered in all directions

Question 17

What is specular reflection?

Answer 17

When light is reflected on a smooth surface so it reflects evenly

Question 18

Give examples of a source of white light?

Answer 18

the sun or lightbulbs

Question 19

What is white light made up of

Answer 19

A mixture of different colours and can be split up into colours using the visible spectrum using a prism

Question 20

What happens when white light hits a coloured surface?

Answer 20

Some colours that make it up are reflected and some are absorbed

Question 21

How does an object become a certain colour?

Answer 21

It absorbs the other colours and reflects the colour it is

Question 22

What does a filter do?

Answer 22

They are pieces of transparent material that absorb some of the colours in white light (e.g blue filters transmit blue light but absorb all the other colours)

Question 23

What is a lens?

Answer 23

A piece of transparent material shaped to refract light in a certain way

Question 24

What does the power of a lens describe?

Answer 24

How much it bends light that passes through it - a more powerful lens is more curved and bends the light more

Question 25

What is a converging lens?

Answer 25

- Fatter in the middle than at the edges | - Makes parallel rays of light converge at the focal point

Question 26

What is the focal length?

Answer 26

The distance between the focal point and the centre of the lens

Question 27

What is a diverging lens?

Answer 27

-Thinner in the middle than at the edges

Question 28

What is the focal point?

Answer 28

The point from which the rays seem to be coming after passing through the lens

Question 29

What is a real image?

Answer 29

An image that can be projected onto a screen

Question 30

How can real images only be formed?

Answer 30

By light rays that come together

Question 31

What is inverted?

Answer 31

Upside down

Question 32

What forms a virtual image?

Answer 32

An object close to a converging lens

Question 33

Why is an image called virtual?

Answer 33

Because it cannot be projected onto a screen

Question 34

What will a diverging lens always produce?

Answer 34

- Virtual images that are the same way up | - Much smaller and closer to the lens than the object

Question 35

What is the name of the frequencies of light that our eyes can detect?

Answer 35

Visible light

Question 36

What type of waves are all EM wave?

Answer 36

Transverse waves

Question 37

Where do all EM waves travel at the same speed?

Answer 37

In a vacuum

Question 38

What do all objects emit energy by?

Answer 38

Infrared radiation

Question 39

What is the order of EM radiation in order of ascending frequency?

Answer 39

Radio waves, microwaves, infrared, UV, X-rays and gamma rays

Question 40

What type of radiation has the longest wavelength?

Answer 40

Radio waves (red)

Question 41

What do most telescopes use to focus the EM radiation onto a central sensor?

Answer 41

Curved mirrors

Question 42

What can visible light be used for?

Answer 42

Light bulbs

Question 43

What can infrared radiation be used for?

Answer 43

Communication at short ranges like computers in the same root or a TV to a remote control unit

Question 44

What can microwaves be used for?

Answer 44

Communication and satellite transmissions, including mobile phone signals

Question 45

What are radio waves used for?

Answer 45

Transmitting radio broadcasts and TV programmes

Question 46

How are radio waves transmitted?

Answer 46

- The radio waves are produced by oscillations in electrical circuits - Metal rod/wire can be used as an aerial to receive the radio waves - The radio waves are absorbed by the metal and cause oscillations in electric circuits connected to the aerial

Question 47

What are oscillations?

Answer 47

Variations in current and voltage

Question 48

What is refraction?

Answer 48

The bending of the path of a wave due to a change in velocity

Question 49

What layer in the atmosphere can cause the refraction of some frequencies of radio waves?

Answer 49

The ioniosphere

Question 50

Are microwaves refracted in the Earth's atompshere?

Answer 50

No

Question 51

Can radio waves be refracted in the Earth's atmosphere?

Answer 51

Yes

Question 52

When does the intensity of radiation emitted by an object increase?

Answer 52

As its temperature increases

Question 53

What is the correlation between temperature and wavelength?

Answer 53

The higher the temperature, the shorter the wavelength

Question 54

What is the power of energy?

Answer 54

The amount of energy transferred in a certain time

Question 55

How does a system stay at a constant temperature?

Answer 55

It must absorb the same amount of power as it radiates

Question 56

Describe the Earth's energy balance

Answer 56

- Earth's surface absorbs about 1/2 of radiation that reaches it from the Sun - Re-radiates this energy as IR radiation, which can warm up the atmosphere - For the temp of the Earth to stay the same, it must radiate energy into space at the same average rate it is absorbed

Question 57

What is the greenhouse effect?

Answer 57

Gases in our atmosphere that naturally absorb some energy, keeping the Earth at a higher temperature than if there were no atmosphere

Question 58

What would happen if some greenhouse gases were removed from the atmosphere?

Answer 58

The atmosphere would be able to hold less energy and its temperature would decrease

Question 59

What can UV radiation be used for?

Answer 59

To disinfect water by killing microorganisms in it

Question 60

What is fluorescence?

Answer 60

Materials that absorb UV radiation and re-emit it as visible light

Question 61

What are fluorescent materials often used for?

Answer 61

Security markings, where the materials are only visible when UV light shines on them

Question 62

What are X-rays used for?

Answer 62

In medicine to make images of inside of the body, as they can pass through muscles and fat easily but bone absorbs some X-rays

Question 63

What are gamma rays used for?

Answer 63

To sterilise food and surgical instruments by killing potentially harmful microorganisms (as they transfer a lot of energy and can kills cells)

Question 64

How can gamma rays be used to detect cancer?

Answer 64

- A chemcial that emits gamma rays is injected into the blood - The chemical is designed to collect inside cancer cells - A scanner outside the body then locates the cancer by finding the source of the gamma rays - Gamma rays can pass through all materials in the body

Question 65

Which type of frequency of waves are more potentially dangerous?

Answer 65

Higher frequency waves, as they transfer more energy

Question 66

How can too much exposure lead to skin cancer?

Answer 66

Sunlight contains high frequency UV radiation, which is transferred to our cells and can cause sunburn and damage DNA, causing a mutation (cancer)

Question 67

What can excessive exposure to X-rays or gamma rays cause?

Answer 67

Mutations in DNA that can kill cells or cause cancer

Question 68

What is EM radiation produced by?

Answer 68

Changes in the electrons or nuclei in atoms

Question 69

What can radiation cause?

Answer 69

Changes in atoms, such as causing atoms to lose electrons to become ions