Unit 2: Lesson 12 - Converging and Diverging Lenses

practice

practice

Q: What does a converging lens do?

A: It brings light rays together to a point after passing through the lens. Example: magnifying glass.

Q: What does a diverging lens do?

A: It spreads light rays apart after passing through the lens. Example: camera lens, door peephole.

Path of Light Through a Lens

Q: How does light behave when passing through a lens?

A: Light refracts twice:

When it enters the lens (air → glass)

When it exits the lens (glass → air)

Q: How can you simplify ray diagrams?

A: Draw a vertical line through the optical centre and show the refracted rays from that line.

Images in Converging Lenses

Q: Where is a real image formed by a converging lens?

A: On the opposite side of the lens from the object.

Images in Diverging Lenses (L.O.S.T method)

Q: What are the L.O.S.T rules for images in diverging lenses

A:

L - Image is on the same side as the object

O - Image is upright

S - Image is smaller than the object

T - Image is virtual

Q: Where is a virtual image formed by a converging lens?

A: On the same side of the lens as the object.

Quick summary for Converging lens? and Diverging Lenses?

- Converging lens: brings rays together → real or virtual images

- Diverging lens: spreads rays apart → always upright, smaller, virtual (use L.O.S.T to remember)

Optical Centre? (Symbol?)

Optical Centre (O) - point at exact centre of lens

Principal axis ?

Principal axis - the line that goes through the optical centre and the centre of the lens

Principal Focus? (Symbol?)

Principal Focus (F) - point on the principal axis where rays parallel to principal axis converge (meet)

Secondary Principal Focus? (Symbol?)

Secondary Principal Focus (F') - focus on the same side of lens as the incident rays

(NOTE: light can strike a lens from?

(NOTE: light can strike a lens from either side)