Lenses Flashcards
What do convex lenses do?
They bulge outwards, causing the rays of light parallel to the axis to converge (be brought together) at the principal focus
a concave lens…
caves inwards, causing parallel rays of light to diverge (spread out)
The principal focus of a convex lens is where…
rays hitting the lens parallel to the axis all meet
The principal focus of a concave lens is…
the point where rays hitting the lens parallel to the axis appear to all come from
Three rules for refraction in a convex lens are…
1) an incident ray parallel to the axis refracts through lens and passes through the principal focus on the other side
2) an incident ray passing through principal focus refracts through the lens and travels parallel to the axis
3) incident ray passing through the centre of the lens carries on in the same direction
Three rules for refraction in a concave lens…
1) incident ray parallel to axis refracts through the lens, and travels in line with the principal focus
2) incident ray passing through lens towards the principal focus refracts through the lens and travels parallel to the axis
3) an incident ray passing through the centre of the lens carries on in the same direction
What is a real image?
where the light from an object comes together to form an image on a ‘screen’
What is a virtual image?
When the rays are diverging, so the light from the object appears to be coming to from a completely different place
Concave lenses always create…
Virtual images
