Light and electromagnetic spectrum - SP5 Flashcards
what does the letter ‘i’ represent on a ray diagram?
angle of incidence
what does the letter ‘r’ represent on a ray diagram?
angle of refraction/reflection
what does a ray diagram represent?
it models what happens when light is reflected/refracted
what is the normal on a ray diagram?
line drawn at a right angle to the barrier/mirror - this is the line that angles of incidence/refraction/reflection are taken from
what is the law of reflection?
when a wave is reflected - the angle of reflection is equal to the angle of incidence
what is total internal reflection?
when the angle of incidence increases so much so that it reaches critical angle - the light is completely reflected inside the glass
what is the angle of incidence at total internal reflection called?
crictical angle
which way does the light ray bend if it goes into amedium where it travels slower?
towards the normal
what direction does the light ray bend if the light ray enters a medium where it travels faster?
away from the normal
how do we see luminous objects vs non-luminous?
luminous - light from them enters our eyes
non-luminous - they reflect light
what is it called when rough surfaces scatter reflected light in all directions?
diffuse reflection
what is white light and how can it be split up into the visible spectrum?
white light - a mixture od different colours of light that our eyes see as white
can be split into visible spectum using a prism
absorbtion and refkection? what aboute white?
how do we percieve colour?
white light hits a coloured surface - some colours are absorbed, some are reflected. The colour it is presented as is reflected and so, reaches our eyes - all other colours are absorbed - white objects reflect all colours
what is a filter and how does it produce coloured light
peice of transparent material that absorbs some colours in white light but transmits (allws through) others
how many types of cone cells do we have that detect light? what 3 colours do the cones detect? - if all are present what is percieved?
3 cone types - red, blue or green - (all present shows white)
what is a lens?
peice of transparent material shaped to refract light in particular ways
what does the power of a lense describe?
what effect do powerful lenses have?
how much it bends light that passes through it - powerful lenses are more curved and hence bend light more
what shape is a converging lense and what does it do?
fatter in the middle than the edges - makes parallel rays of light converge at the focal point - narrows the light to a point
what is the focal length?
distance between focal point and the centre of the lens
what shape is a diverging lens and what does it do?
thinner in the middle than at the edges - spreads out parallel rays
what are the uses of a converging lense?
- used to focus rays of light onto a screen to form a reduced real image of a distant object
- used to focus rays of light to form a magnified virtual image of a near object
when can real images be formed only?
when rays of light come together
what type of wave is light?
electromagnetic
how are different frequencies of light percieved by our eyes?
as visible light
what are frequencies that are higher than visible light called?
ultra violet
what type of wave are all electromagnetic waves?
transverse
what speed do electromagnetic waves travel in a vacum?
3x10(8) m/s
what do electromagnetic waves do to get light to an observer?
transfer energy from a source
