Light and the EM Spectrum - topic 4 Flashcards
what happens when a light ray hits the surface
it reflects off the surface
what is the law of reflection
the angle of incidence = angle of reflection
what is refraction
the change in direction of a wave passing from one medium to another is caused by its change in speed
what happens if the light wave is going from a less dense medium to a more dense medium
propagation of light will slow down and will bend towards the normal
what are the 2 types of reflection
specular reflection and diffuse reflection
diffuse diffusion
what is specular reflection
when reflection is perfect due to reflection from the smooth surface
what is diffuse reflection
reflection is imperfect due to a rough surface
colours of visible light from longest to shortest
red
orange
yellow
green
blue
indigo
violet
why are all colours revealed when white light passes through a prism
all colours individually have different wavelengths and travel at different speeds so are refracted by different amounts
what happens when white light hits a coloured surface
white light is absorbed along with all of its colours aside from the colour of the object
what are the two types of lenses
convex
concave
what type of image does convex lens form
real image
what type of image does concave lens form
virtual image
what type of waves are EM waves
transverse waves
order of EM waves from longest to shortest
radiowaves, microwaves, infrared, visible, ultraviolet, x-rays, gamma rays
the higher in temp an object is……
the more infrared radiation it emits
amount of energy the object absorbs must be……
the same as the amount of energy the object radiates
what colour is the best emitter and absorber of infrared radiation
Matte Black
what colour is the best reflector of infrared radiation
white
harmful effects of microwaves
internal heating of body cells
harmful effects of infrared
skin burns
harmful effects of UV light
damage to skin cells and eyes, leading to skin cancer and eye conditions
harmful effects of x-rays/ gamma rays
mutation/damage to cells in the body
uses of radio waves
broadcasting, communications, satellite transmissions
uses of microwaves
cooking, communication, satellite transmissions
conditions for total internal refraction
light ray has to go from more to less dense medium
the angle of incidence has to be greater than the critical angle
uses of infrared
cooking, thermal imaging, short-range communication, tv remote controls
uses of visible light
vision, photography
uses of UV
security markings, disinfecting water, detecting forged banknotes
uses of x-rays
airport security scanners, medical x-rays
uses of gamma rays
sterilising food and medical equipment and detecting cancer and its treatment
what is total internal reflection
where the ray is reflected back into the first material instead of being transmitted into the new material
what are the two types of lenses
converging and convex
what is focal length
the distance from the centre of a lens to its principal focus
what type of images do converging lens form
real images
what type of images are formed by diverging lens
Upright, diminished and virtual images
when is a real image formed
when the light rays from a point on an object come together to form an image
when are virtual images formed
when light rays don’t actually come together to form an image
what do you need to say when describing an image
how big it is compared to the object
whether it is upright or inverted
whether it is real or virtual
how does the focal length and shape of a lens affect its power
the shorter the focal length and the more curved the lens is, the more powerful the lens
differences between converging and diverging lenses
converging lenses can produce real or virtual images and diverging can only produce virtual images
converging lens converge light, diverging lens diverge lens
what speed do EM waves travel at in a vacuum
at the same speed
what happens if the average power emitted by an object is larger than the average power absorbed by the object
the object will cool down
what happens if the average power emitted by an object is smaller than the average power absorbed by the object
the object heats up
what colour is the best absorber and emitter of radiation
black
what type of surface is the best absorber and emitter of radiation
matt
when does total internal reflection occur
when a wave is travelling into a less dense material
AND when the angle of incidence is larger than the critical angle
what types of wave is a sound wave
longitudinal
what type of wave is a light wave
transverse
what speed do all EM waves travel at in a vacuum
3x10^8 m/s
what happens if an atom absorbs energy
some of its electrons move to higher energy levels
what happens when each electron falls back down to a lower level
an em wave is produced
when are gamma rays produced
when there’s a change in the nuclei of atoms
when are gamma rays emitted
when the nucleus needs to get rid of extra energy
how are radio waves produced
using an alternate current in an electrical circuit .
As charges oscillate they produce oscillating electric and magnet fields.
what does intensity and wavelength distribution depend on
their temperature
