Topic 6 Lenses Flashcards
How do lenses form images
By refracting light
Convex lense
Bulges outwards
Causes rays of light parallel to the axis to be brought together (converge) at the principle focus
Concave lenses
Cave inwards
Causes parallel rays of light to spread out (diverge)
What is the axis of a lense
The line passing through the middle of the lens
What is the principle focus of a Convex lens
Where rays hitting the lens parallel to the axis all meet
What is the principle focus of a concave lens
The point where rays parallel to the axis appear to come from and can race them back until the appear to meet up
What is the focal length
Distance from centre of lens to principle focus
3 rules for convex lenses
And incident ray parallel to the axis refracts through the lens and passes through the principal focus on the other side
an incident ray passing through the principal focus refracts through the lens and travels parallel to the axis
an incident passing through the centre of the lens carries on in the same direction
3 rules for concave lens
An incident ray parallel to the axis refracts through the lens and travels in a line with the principal focus
an incident ray passing through the lens towards the principle focus refracts through the lens and travels parallel to the axis
An incident ray passing through the centre of a lens carries on in the same direction