Topic 5 Flashcards
explain the rules of total internal reflection
- if angle < critical angle: light refracts away from normal
- if angle = critical angle: light passes along boundary
- if angle > critical angle: light reflects [TIR]
Explain the difference between specular and diffuse reflection
- specular has smooth surface, diffuse has a rough surface
- specular can reflect light ,diffuse can refract light
describe how a student could use semi-circular glass block to determine the critical angle
- 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
Explain how colour of light is related to differential absorption at surfaces
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
Explain how colour of light is related to transmission of light through filters
- 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
Relate the power of a lens to its focal length and shape
- power the lenses inverse the focal length
- shorter focal length ,greater power
- thicker lenses means shorter focal length
what are the similarities and differences in the refraction of light by converging and diverging lenses
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.
Explain the effects of different types of lens in producing real
and virtual images
- 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.
what are electromagnetic waves?
- transverse waves
- travel at the same speed in a vacuum
explain, with examples, that all electromagnetic waves
transfer energy from source to observer
microwave source to food
name the EM waves in order
radio waves, microwaves, infrared, visible, ultraviolet, x-rays and gamma rays
how is the EM described as and what is pattern?
- continuous
- radio waves have the long wavelength and short frequency
- gamma rays have a short wavelength and high frequency
Explain the effects of differences in the velocities of electromagnetic waves in different substances
violet is the SLOWEST bc refracts the most (ultra violet)
res is the FASTETS bc reflects less (infrared)
Explain that for a body to be at a constant temperature..
it needs to radiate the same average power that it
absorbs
Explain that all bodies emit radiation, that the intensity and
wavelength distribution of any emission depends on
temperature
Explain how the temperature of the Earth is affected by
factors controlling the balance between incoming
radiation and radiation emitted?
- 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
Explain what happens to a body if the average power it
radiates is less or more than the average power that it
absorbs?
if object absorbed more power than emits- temp increase
if object absorbed less power than it emits - temp decreases
what are potential danger associated with an electromagnetic wave increases with increasing frequency?
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
what are some uses of radio waves
- including broadcasting
- communications
- satellite transmissions
what are some uses of microwaves
- including cooking
- communications
- satellite transmissions
what are some uses of infrared
- including cooking
- thermal imaging
- short range
- communications
- optical fibres
- television remote controls
- security systems
what are some uses of visible light
- including vision
- photography
- illumination
what are some uses of ultra violet
- including security marking
- fluorescent lamps
- detecting forged bank notes
- disinfecting water
what are some uses of x-rays
- including observing the internal structure of objects
- airport security scanners
- medical x-rays
