Topic 6 Lenses

Question 1

How do lenses form images

Answer 1

By refracting light

Question 2

Convex lense

Answer 2

Bulges outwards
Causes rays of light parallel to the axis to be brought together (converge) at the principle focus

Question 3

Concave lenses

Answer 3

Cave inwards
Causes parallel rays of light to spread out (diverge)

Question 4

What is the axis of a lense

Answer 4

The line passing through the middle of the lens

Question 5

What is the principle focus of a Convex lens

Answer 5

Where rays hitting the lens parallel to the axis all meet

Question 6

What is the principle focus of a concave lens

Answer 6

The point where rays parallel to the axis appear to come from and can race them back until the appear to meet up

Question 7

What is the focal length

Answer 7

Distance from centre of lens to principle focus

Question 8

3 rules for convex lenses

Answer 8

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

Question 9

3 rules for concave lens

Answer 9

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