Lenses Flashcards
what does a converging lens look like (convex)
bulges outwards
what does a diverging lens look like (concave)
caves inwards
what does a converging lens do
causes rays of light parallel to the axis to converge at the principle focus (brought together)
what does a diverging lens do
causes parallel rays of light parallel to the axis to diverge (spread out)
what is the focal length
distance from center of lens to the principle focus
what is a real image
where the light coming from an object comes together to form an image on the screen
what is a virtual image
when rays are diverging so the light from the object appears to be coming from a completely different place
what type of image does a magnifying glass show
- a magnifying glass shows a virtual image
- because the point at which the object seems to have been created isnt actually the point in which the light rays meet
what type of image does an eye form
- a real image
- because of the image formed on the retina
what is the axis of a lens
the line going through the middle of the lens
what is the principle focus of a converging lens
where the rays hitting the lens parallel to the axis all meet
what is the principle focus of a diverging lens
- the point where rays hitting the lens parallel to the axis appear to all come from
- you can trace them back until they all appear to meet up at a point behind the lense
how do light rays act when going through a lens in general
- when they enter the lens, they bend towards the normal due to the change in density (going into a more dense area)
- but when they leave the lens from the other side, they refract away from the normal due to the change in density (going into a less dense area)
when are images formed
at points when all the light rays coming form something seem to come together at one point
why can a real image be captured on screen
because the light rays actually meet at the place the image seems to be
why cant a virtual image be captured on a screen
because the light rays dont actually come together at the point the image seems to be
what is the focal length related to and what does it mean
- the power of the lens
- it means that the more powerful the lens
- the more strongly it converges the rays of light
- so the shorter the focal point is from the center of the lense
what are the powers in a converging and diverging lense
- the power in a converging lens is positive
- the power in a diverging lens is negative
what are the two ways in which you can make a more powerful lens
- by increasing the curvature of the lens or making it with more strongly curved surfaces
- or by using materials that are better at focusing light than others
what is the effect of a more powerful lens being able to be created by changing the material in which it ia made from
it means that a more powerful lens can be created that is thinner simply by changing the material it is made from
