Light: Refraction, Lenses, and Reflection

Question-and-answer flashcards covering convex lenses, refraction, optical illusions, reflection, and periscope operation.

What effect does a convex lens have on parallel light rays?

It bends (refracts) them inward so they converge at the focal point.

Which common vision problem is corrected with convex lenses?

Long-sightedness (hyperopia).

Name three optical devices that use convex lenses.

Eyeglasses, microscopes, and telescopes (also projectors and binoculars).

What is the basic definition of a lens?

A transparent substance with at least one curved surface that bends light.

Define refraction.

The bending of light as it passes from one medium to another because its speed changes.

Why can objects appear bigger or smaller when viewed through a lens?

Because refraction makes light rays change direction, so the rays seem to come from a different point than the actual object.

What is an optical illusion?

Something the eyes see that isn’t actually how the object exists in reality.

Why does a pencil look bent or enlarged in a glass of water?

Refraction: light slows down in water, bending the rays and altering the pencil’s apparent position and size.

What surfaces are best at reflecting light?

Smooth, polished surfaces such as plain mirrors or clear still water.

What is reflected light?

Light that bounces off a surface rather than passing through it or being absorbed.

What instrument uses two mirrors to allow sight over or around obstacles, and what principle does it rely on?

A periscope; it relies on the reflection of light.

Describe the path of light inside a periscope.

Light reflects off the observed object to the top mirror, then down the tube to the bottom mirror, and finally into the viewer’s eye.