Optics

Starter

Can you complete this diagram?

What is this shape of lens called?

Principal axis

Learning Objectives

• Know key terms related to convex lenses.

• Know the effect of a convex lens on: a diverging beam of light, a parallel beam of light.

• Know how a camera and projector produce an image.

• Know how to find the size of an image.

Success criteria• Describe the effect of a convex lens

on: a diverging beam of light, a parallel beam of light having done an experiment. (Grade C)

• Explain the difference between a camera and projector. (Grade C)

• Use scale diagrams to find image sizes. (Grade A)

Convex lenses• Convex lenses are also called

converging lenses, because they bring light rays together to a focal point.

• The focal length is measured from the centre of the lens to the focal point.

• Measure the focal length on your diagram.

Thicker Lenses

• Thicker lenses bend light more, and so are more powerful – they have shorter focal lengths. What about the eye?

Uses of convex lenses• Convex lenses are used in:• Telescopes• Cameras• The thing which is allowing you to

read this!

They use convex lenses to focus what is called a real image.

Real Images

• Projectors and cameras both produce real images.

• Light from the object actually reaches a screen or film.

Ray Diagrams

Learning Objectives

• Know key terms related to convex lenses.

• Know the effect of a convex lens on: a diverging beam of light, a parallel beam of light.

• Know how a camera and projector produce an image.

• Know how to find the size of an image.

Success criteria• Describe the effect of a convex lens

on: a diverging beam of light, a parallel beam of light having done an experiment. (Grade C)

• Explain the difference between a camera and projector. (Grade C)

• Use scale diagrams to find image sizes. (Grade A)

Plenary

ANSWERS:a) Ab) B

a) Which diagram represents a camera?b) Which diagram represents a slide projector?