2.11 - Convex and Concave Lenses

What is a lens?

a shaped piece of transparent glass or plastic that refracts light

What are lenses used for?

• cameras

• telescopes

• binoculars

• microscopes

• corrective glasses

What are convex lenses?

an object or shape that curves or bulges outwards, like a circle or sphere

How do convex lenses look?

is thicker in the middle than it is at the edges

What happens to light rays that enter the lens?

• parallell light rays that enter the lens converge

• they come together at a point called the principal focus

What does converge mean?

move towards rach other

What is the principal focus?

the focus of a lens where light rays appear to converge or to diverge from

What is the principal focus also known as?

the focal point

What part of the convex lens is 1?

convex

What part of the convex lens is 2?

principal focus

How is convex lens drawn in a ray diagram?

a convex lens is drawn as a vertical line with outward facing arrows to indicate the shape of the lens

What is the focal length?

the distance from the lens to the principal focus

What part of the ray diagram is 1?

principal axis

What part of the ray diagram is 2?

focal length

What part of the ray diagram is 3?

principal focus

What is a concave lens?

an object or shape that curves inwards rather than bulging outwards

How do convave lenses look?

thinner in the middle than it is at the edges

What happens to light rays that enter the concave lens?

• this causes parallel rays to diverge

• they separate but appear to come from a principle focus on the other side of the lens

What does diverge mean?

when a light ray splits up or spreads out

What part of a concve lens is this?

concave lenses

How are concave lenses drawn in a ray diagram?

as a vertical line with inward facing arrows to indicate the shape of the lens

What part of the ray diagram is 1?

principal axis

What part of the ray diagram is 2?

focal length

What part of the ray diagram is 3?

principal focus