Topic 5 - light and the electromagnetic spectrum

Question 1

What is total internal reflection?

Answer 1

When a light is completely reflected back at a boundary between two mediums
It occurs when light meets a less dense medium at an angle of incidence larger than the critical angle

Question 2

What is the critical angle?

Answer 2

The angle of incidence which causes the angle of reflection to be 90 degrees

Question 3

What determines the colour of visible light waves?

Answer 3

The wavelength and frequency of the light waves

Question 4

What colour of visible light has the highest frequency?

Answer 4

Blue

Question 5

What colour of visible light has the largest wavelength?

Answer 5

Red

Question 6

What is meant by ‘speculate reflection’?

Answer 6

Rays are reflected from a smooth surface in a single direction

Question 7

WhT is meant by ‘diffuse reflection’?

Answer 7

Reflection from a rough surface which causes scattering

Question 8

How does a red colour filter work?

Answer 8

A red filter absorbs all wavelengths of light other than those in the red range of the spectrum
So only red light passes through

Question 9

What is meant by ‘opaque’?

Answer 9

Not see through

Question 10

What governs the colour of an opaque object?

Answer 10

Different objects reflect different wavelengths of light by different amounts
The wavelengths that are most strongly reflected determine the colour

Question 11

What happens to the wavelengths of light that aren’t reflected by any opaque object?

Answer 11

Any wavelengths that aren’t reflected are absorbed by the object

Question 12

What colour does an object appear if all wavelengths are reflected by equal amounts?

Answer 12

White

Question 13

What colour does an object appear if all wavelengths are absorbed?

Answer 13

Black

Question 14

What type of waves are electromagnetic waves?

Answer 14

Transverse

Question 15

What do electromagnetic waves transfer?

Answer 15

Energy (not matter))

Question 16

What type of spectrum do electromagnetic waves form?

Answer 16

A continuous spectrum

Question 17

List the order of the electromagnetic spectrum in order of increasing wavelength

Answer 17

Gamma, X-rat, Ultraviolet, visible, infrared, microwaves, radio

Question 18

What is the highest frequency electromagnetic wave?

Answer 18

Gamma waves

Question 19

What is the highest energy electromagnetic wave?

Answer 19

Gamma waves

Question 20

What properties are shared by all electromagnetic waves?

Answer 20

All transverse
All travel at 3x10^8 m/s
Can all travel through a vacuum

Question 21

What range of frequencies of electromagnetic waves can be detected by the human eye?

Answer 21

400-700 manometers

Question 22

How do the speeds of EM radiation differ in a vacuum and in air?

Answer 22

They travel at the same speed

Question 23

What can happen when radiation strikes an object?

Answer 23

It can be transmitted, reflected or absorbed

Question 24

What do all objects emit and absorb?

Answer 24

Infrared radiation

Question 25

WhT happens to the quantity of infrared radiation emitted by an object as temperature increases?

Answer 25

The hotter the object, the more infrared radiation it will emit

Question 26

What happens to the type of radiation emitted bu an object as temperature increases?

Answer 26

The hotter the body the shorter the wavelength of radiation releases

Question 27

What is required for an object to be at a constant temperature?

Answer 27

The body would need to emit radiation at the same rate it absorbs it - it needs to radiate at the same average power that it absorbs

Question 28

What is meant by intensity?

Answer 28

The power transferred per unit area, it is a measure of the energy transferred by a wave

Question 29

What will happen if the average power that an object radiates is less than it absorbs?

Answer 29

The temperature of the object will decrease

Question 30

Hat can be said about the rates of emission and absorption for an object increasing in temperature?

Answer 30

The object is absorbing radiation faster than it is emitting it

Question 31

Give two factors that affect the temperature of the earth

Answer 31

The amount of reflection of radiation into space | The earth”’s rate of absorption and emission of radiation

Question 32

How does the Earth’s atmosphere effect radiation?

Answer 32

It absorbs of reflects radiation from the sun, preventing it from reaching earth Some is allowed to pass through and warms the earth

Question 33

What happens to the radiation emitted from the earth?

Answer 33

It is absorbed and re-emitted in all direction but greenhouse gases, resulting in the greenhouse effect which warms the earth

Question 34

What type of waves can be produced by oscillations in an electrical circuit?

Answer 34

Radio

Question 35

How can radio waves created an alternating current in a circuit?

Answer 35

When they are absorbed, they induce oscillations in a circuit with the same frequency as the waves themselves

Question 36

Where do gamma rays originate from?

Answer 36

Changes in the nuclei of atoms

Question 37

What health effects can untraviolet waves cause?

Answer 37

Premature skin aging | Can increase the risk of developing skin cancer

Question 38

What health effects can X-rays and gamma rays cause?

Answer 38

Are ionising radiation so can cause mutations in genes | Can lead to increased risk of developing various cancers

Question 39

What health effects can infrared rays cause?

Answer 39

Can cause burns to skin/tissue

Question 40

How does electromagnetic radiation affect electron arrangement in atoms?

Answer 40

Absorption or emission of em radiation can cause electron arrangement to change

Question 41

How do atoms become ions?

Answer 41

By losing or gaining outer electrons

Question 42

What are the effects of body cells absorbing radiation?

Answer 42

Large amounts can damage cells | Smaller amounts cause mutation, Causing cells to divide rapidly, which can lead to cancer

Question 43

State and explain the main use of radio waves

Answer 43

Communication | Because they are long wavelength and can travel long distances without losing quality

Question 44

State and explain the main use of microwaves

Answer 44

Cooking, as microwaves are absorbed by and heat fat/water in foods

Question 45

State uses of infrared radiation

Answer 45

Cooking food Infrared cameras Short range communication

Question 46

State and explain uses of UV radiation

Answer 46

Sterilisation, as it kills bacteria Energy efficient lamps, as it radiates low heat but high energy Sun tanning

Question 47

State and explain uses of X-rays

Answer 47

Medical imaging and treatment p, because they are very high energy and can easily penetrate body tissues

Question 48

State a use of gamma rays

Answer 48

Medical treatments, such as radiotherapy in the treatment of cancer

Question 49

Which waves of the EM spectrum are regarded as most dangerous?

Answer 49

Gamma and X-rays as they have the highest energy