SP5 - Light And The Electromagnetic Spectrum ✓

Question 1

SP5a - What two processes can be shown using a ray diagram?

Answer 1

Reflection
Refraction

Question 2

SP5a - What do i and r represent in ray diagrams?

Answer 2

i: Angle of incidence (between incident ray and the normal)
r: Angle of reflection/refraction (between reflected/refracted ray and the normal)

Question 3

SP5a - What is the relation between the angles of incidence and reflection/refraction?

Answer 3

i = r (Angle of incidence = angle of reflection/refraction)

This is the law of reflection

Question 4

SP5a - What is the normal?

Answer 4

The line drawn perpendicular to the object light is reflecting off (or refracting through)

Question 5

SP5a - Describe total internal reflection.

Answer 5

TIR occurs when light refracts through a substance at sucha low angle of incidence that it doesn’t leave the other side
This angle is called the critical
If light enters at the critical, it will move along the interface
If light enters at an angle smaller than the critical, it will cause TIR to happen

Question 6

SP5a CP - Describe a method to explore refraction with varying angles of incidence.

Answer 6

Place a ray box with a slit in front of it on a piece of paper
Place a glass box the way of the ray of light thta is being produced
Draw around the glass block
Mark the point of entry and exit for the light aswell as two further points (such as origin and edge of paper) on the piece of paper
Use your markings to draw lines representing the travel of the ray of light
Repeat with ray box at different angles and compare your results

Question 7

SP5b - What are the two types of reflection?

Answer 7

Specular: When light is reflected evenly on a smooth surface
Diffuse: When light is reflected in all directions on a rough surface

Question 8

SP5b - Describe why a green object appears green in sunlight.

Answer 8

Sunlight is made up of white light as it contains all the colours of the visible spectrum
An object that appears green will reflect the green part of the spectrum but reflect all the other colours

Question 9

SP5b - what effect would a blue filter have?

Answer 9

A blue filter would only transmit the blue part of the light that goes to it.

Question 10

SP5d - What are the similarities between all EM waves?

Answer 10

They are all transverse waves
They all travel at (3x10^8m/s) ina vacuum
They transfer energy

Question 11

SP5d - How were infrared waves discovered?

Answer 11

A prism was used to refract white light into the seven componenets.
A thermometer was placed just outside of the red part of this spectrum.
Another was placed in the spectrum.
The thermometer next to red was warmer suggesting there was something warming it up

Question 12

SP5e - List all the colours in the visible light spectrum.

Answer 12

ROYGBIV

Red
Orange
Yellow
Green
Blue
Indigo
Violet

Question 13

SP5e - List all of the EM waves in order of increasing wavelength/decreasing frequency.

Answer 13

Gamma rays
X-rays
Ultraviolet
Visible light
Infrared
Microwaves
Radio waves

Question 14

SP5e - Why do different telescopes need to be used to study different EM waves?

Answer 14

EM waves of different length get absorbed by different amounts by the atmosphere

Question 15

SP5f - What can infrared be used for?

Answer 15

Heating food
Short range communication such as TV remotes
Security systems

Question 16

SP5f - What can microwaves be used for?

Answer 16

Communications and satellite transmissions
Heating up food and giving it energy

Question 17

SP5f - What can radio waves be used for?

Answer 17

Transmitting radio broadcasts
Radio communications via satellites

Question 18

SP5f - How are radio waves produced?

Answer 18

Oscillations in electrical signals.
Metal rods can be used as aerials because they can absorb and transmit these oscillations

Question 19

SP5f - Whay can radio waves be used for longer ranges than microwaves?

Answer 19

The way radio waves and microwaves travel is dependant on the angles they reach the ionosphere.
At all angles, microwaves pass straight through and so there is maximum range they can be fired in a straight line.
At some angles, radio waves are reflected by the ionosphere, becasue they have larger wavelengths.
This means they don’t have to be fired directly to a point

Question 20

SP5h - What are the uses of Ultraviolet rays?

Answer 20

Disinfect waters by killing microorganisms
Invisible ink due to fluoresence
Security on bank notes

Question 21

SP5h - What are the uses of x-rays?

Answer 21

Imaging of the inside of the body

Question 22

SP5h - What are the uses of gamma radiation?

Answer 22

Radiotherapy
Sterilisation of medical equipment and food
PET scanner

Question 23

SP5i - What are the dangers of infrared radiation?

Answer 23

Infrared radiation is absorbed by our body.
We feel it as heat and an excess of it can destroy cells burning skin

Question 24

SP5i - What are the dangers of ultraviolet light?

Answer 24

It can cause sunburn and damage to DNA which can lead to skin cancer

Question 25

SP5i - What are the dangers of x-rays and gamma rays?

Answer 25

They can lead to mutations causing cancer.

Question 26

SP5i - Why are UV x-rays and gamma rays dangerous?

Answer 26

They are ionising radiation.
They large amounts of energy due to high frequencies and short wavelengths which can pass through our skin.

Question 27

SP5g - What is the difference between a hot and cold object in terms of radiation?

Answer 27

All objects emit the same amount of radiation that they absorb.
Hotter objects will emit more radiation than cold objects in the same time

Question 28

SP5g - For the earth’s temperature to stay constant what must happen?

Answer 28

The amount of radiation it absorbs from the sun must be equal to the amount of radiation that the earth radiates into space

Question 29

SP5g - Describe the greenhouse effect in terms of radiation.

Answer 29

Energy from the sun is absorbed by the earth.
The earth radiates this into the atmosphere
Greenhouse gases in the atmosphere absorb this energy keeping it in the atmosphere
This means that the earth doesn’t radiate into the atmosphere the same amount of energy it absorbed
Thus the temperature of the earth rises

Question 30

SP5g CP - Describe an experiment to explore how different surfaces absorb and emit infrared radiation using the following surfaces:

Shiny black
Shiny silver
Dull black
Dull grey

Answer 30

Pour water at 80° into four boiling tubes
Cover each with one of the surfaces
Put a thermometer in each
Time it and record the temperautre at regular intervals
The one that has the largest drop in temperature emits the most energy and thus must also absorb the most energy
You would expect the results to be from largest to smallest change:
Dull grey
Dull black
Shiny black
Shiny silver

Question 31

SP5c - What is a lens, and what is its power?

Answer 31

A lens is a small piece of transparent material made to refract light in a certain way

The power of a lens is how much it refracts light and is dependant on the shape and thickness of the lens

Question 32

SP5c - What is the difference between a converging (convex) and diverging (concave) lens?

Answer 32

Converging: Fatter in the middle and thinner at the top and bottom. Rays of light converge onto a focal point
Diverging: Fatter at the top and bottom and thinner in the middle. Rays diverge away from each other once they pass through

Question 33

SP5c - What does F mean on a ray diagram?

Answer 33

F is the focal length, i.e the length between the lens and its focal point

Question 34

SP5c - When an object is placed more than 2F from a converging lens, what happens?

Answer 34

Real image
Inverted
Less than 2F from other side of lens
Smaller size
(camera, eyes)

Question 35

SP5c - When an object is placed at 2F from a converging lens, what happens?

Answer 35

Real image
Inverted
2F from other side of lens
Same size
(Photocopier)

Question 36

SP5c - What happens when an object is placed between 2F and F from a converging lens?

Answer 36

Real image
Inverted
More than 2F from other side of lens
Larger size
(Projector)

Question 37

SP5c - What happens when an object is placed less than F from a converging lens?

Answer 37

Virtual image
Right way up
Further than F on the same side of the lens
Larger size
(Magnifying glass, mirror)

Question 38

SP5c - What happens when an object is placed more than F from a diverging lens?

Answer 38

Virtual image
Right way up
Less than F on the same side
Smaller size

Question 39

SP5c - What is the difference between real and virtual images?

Answer 39

Real images:
- Can be projected onto a screen
- Same way round
- Appears on the opposite side of the lens
- Only produced by converging lenses
- e.g. Projectors

Virtual images:
- Can’t be projected onto a screen
- Inverted (left-to-right)
- Appears on the same side of the lens
- Produced by diverging and converging lenses depending on situation
- e.g. Mirrors

Question 40

SP5c - What is the focal point of a lens?

Answer 40

The point where all the rays of light would converge onto and meet.