Chapter 13-Lenses and Optical Devices

What is a lens?

A transparent object that refracts light to form an image.

What is a converging lens?

A convex lens thicker in the center, focusing rays to a point.

What is a diverging lens?

A concave lens thinner in the center, spreading rays outward.

What is the focal length?

The distance from the lens center to the focal point.

What is the principal axis (lens)?

The straight line passing through the centre of curvature and focal point.

What is the principal focus?

The point where parallel rays converge (or appear to diverge).

What is a ray diagram?

A drawing showing how rays pass through lenses or reflect off mirrors.

What is magnification?

The ratio of image size to object size.

What is the near point?

The closest point at which the eye can focus clearly.

What is farsightedness (hyperopia)?

Can see distant objects clearly; needs converging lenses.

What is nearsightedness (myopia)?

Can see near objects clearly; needs diverging lenses.

What is presbyopia?

Age-related reduced lens flexibility, causing difficulty focusing on close objects.

How do you describe images using S.A.L.T.?

Size, Attitude (upright/inverted), Location, Type (real/virtual).

How does the eye work as a lens?

It acts as a converging lens focusing light on the retina.

How do corrective lenses work?

They adjust how light focuses on the retina to correct vision.

What optical devices use lenses?

Cameras, projectors, microscopes, telescopes, binoculars.