Topic 5

Question 1

explain the rules of total internal reflection

Answer 1

• if angle < critical angle: light refracts away from normal
• if angle = critical angle: light passes along boundary
• if angle > critical angle: light reflects [TIR]

Question 2

Explain the difference between specular and diffuse reflection

Answer 2

• specular has smooth surface, diffuse has a rough surface
• specular can reflect light ,diffuse can refract light

Question 3

describe how a student could use semi-circular glass block to determine the critical angle

Answer 3

• shine a ray into the block
• into the block though the curved face along the radius
• move ray box until angle of refraction is 90 degrees
• measure the angle of incidence
• repeat measure of critical angle

Question 4

Explain how colour of light is related to differential absorption at surfaces

Answer 4

opaque material only allows one colour to be emitted when white light entered the rest would be absorbed,

Black would be absorbed all colours and emit nothing

Question 5

Explain how colour of light is related to transmission of light through filters

Answer 5

• white light is light that is composed of all the colours of visible light
• each colour is a different wavelength and frequency
• a filter is a material that transmits and reflects only one colour of the light. All colours except that transmitted colours were absorbed

Question 6

Relate the power of a lens to its focal length and shape

Answer 6

• power the lenses inverse the focal length
• shorter focal length ,greater power
• thicker lenses means shorter focal length

Question 7

what are the similarities and differences in the refraction of light by converging and diverging lenses

Answer 7

similarities : the both meet at a focal point
differences:
-diverging causes parallel light to spread out from a point
- converging causes parallel light rays to focus and meet at a point.

Question 8

Explain the effects of different types of lens in producing real
and virtual images

Answer 8

• the rays of light from a converging lens can be focusses/captured on a screen, this called a real image
• the focal point of a diverging lenses can not be captured on screen , this is called a virtual image.

Question 9

what are electromagnetic waves?

Answer 9

• transverse waves
• travel at the same speed in a vacuum

Question 10

explain, with examples, that all electromagnetic waves
transfer energy from source to observer

Answer 10

microwave source to food

Question 11

name the EM waves in order

Answer 11

radio waves, microwaves, infrared, visible, ultraviolet, x-rays and gamma rays

Question 12

how is the EM described as and what is pattern?

Answer 12

• continuous
• radio waves have the long wavelength and short frequency
• gamma rays have a short wavelength and high frequency

Question 13

Explain the effects of differences in the velocities of electromagnetic waves in different substances

Answer 13

violet is the SLOWEST bc refracts the most (ultra violet)
res is the FASTETS bc reflects less (infrared)

Question 14

Explain that for a body to be at a constant temperature..

Answer 14

it needs to radiate the same average power that it
absorbs

Question 15

Explain that all bodies emit radiation, that the intensity and
wavelength distribution of any emission depends on

Answer 15

temperature

Question 16

Explain how the temperature of the Earth is affected by
factors controlling the balance between incoming
radiation and radiation emitted?

Answer 16

• infra red from the sun to the earth
• some reflected by the atmosphere some are absorbed into he atmosphere
• energy is absorbed and re-emitted infrared radiation
• it is absorbed by the atmosphere keeps the earth warm

Question 17

Explain what happens to a body if the average power it
radiates is less or more than the average power that it
absorbs?

Answer 17

if object absorbed more power than emits- temp increase
if object absorbed less power than it emits - temp decreases

Question 18

what are potential danger associated with an electromagnetic wave increases with increasing frequency?

Answer 18

MICROWAVES: internal heating of body cells

INFRARED: skin burns

ULTRAVIOLET: damage to surface cells and eyes, leading to
skin cancer and eye conditions

X-RAY AND GAMMA RAYS: mutation or damage to cells in the
body

Question 19

what are some uses of radio waves

Answer 19

• including broadcasting
• communications
• satellite transmissions

Question 20

what are some uses of microwaves

Answer 20

• including cooking
• communications
• satellite transmissions

Question 21

what are some uses of infrared

Answer 21

• including cooking
• thermal imaging
• short range
• communications
• optical fibres
• television remote controls
• security systems

Question 22

what are some uses of visible light

Answer 22

• including vision
• photography
• illumination

Question 23

what are some uses of ultra violet

Answer 23

• including security marking
• fluorescent lamps
• detecting forged bank notes
• disinfecting water

Question 24

what are some uses of x-rays

Answer 24

• including observing the internal structure of objects
• airport security scanners
• medical x-rays

Question 25

what are some uses of gamma rays

Answer 25

• including sterilising food
• medical equipment
• the detection of cancer and its treatment

Question 26

How are radio waves produced?

Answer 26

• radio waves are produced by variations in the current and voltage
• these are called oscillations in electrical circuits
• a metal rod can then be used as an areal
• bc it absorbs radio waves and cause oscillations in circuit connected to the aerial

Question 27

Recall that changes in atoms and nuclei can..

Answer 27

• generate radiations over a wide frequency range
• be caused by absorption of a range of radiations