Life Science Chapter 2 Section 3 Study Guide
Dr. Karoline Rostamiani
Reflection and Refraction (pages 52-60)
Key Terms
Reflection
Law of reflection
Plane mirror
Image
Virtual image
Concave mirror
Optical axis
Focal point
Real image
Convex mirror
Refraction
Lens
Convex Lens
Concave Lens
Objectives
State the law of reflection.
Explain why light rays bend as they enter a new medium at an angle.
Explain what determines the types of images formed by convex and concave lenses.
Reflection (Page 53)
Key Concept: The law of reflection states that the angle of incidence equals the angle of reflection.

When light waves hit a shiny surface, they bounce back. The bouncing back of light waves is
called reflection.

All waves obey the law of reflection.

A wave that is moving toward a surface is the incoming wave.

The wave that bounces off the surface is the reflected waves.

The law of reflection states that the angle the incoming wave makes with the surface is equal to
the angle the reflected wave makes with the surface.
Mirrors (Pages 54-56)
Life Science Chapter 2 Section 3 Study Guide

A plane mirror is a flat sheet of glass that has a smooth, silver-colored coating on the back. The
coating reflects all the light that hits it.

What you see when you look in a mirror is an image.
o

An image is a copy of an object.
The image you see in a plane mirror is called virtual image.
o
A virtual image is an image that forms where the light seems to come from. The image
looks as though it is behind the mirror. A virtual image is always right side up.
Concave mirror

A concave mirror is a mirror that curves inward like the inside of a bowl.

A concave mirror reflects light rays toward the center of the mirror.

The light rays all meet at the same point, called the focal point.
o
The focal point is on the optical axis, an imaginary line that divides a mirror in half.

A concave mirror forms a virtual image if the object is between the mirror and the focal point.

It forms a real image if the object is farther from the mirror than the focal point.
o
A real image forms when reflected light rays meet.
o
A real image is always upside down.
Convex mirror

A convex mirror is a mirror with a surface that curves outward like the outside of a bowl.

Convex mirror reflects light rays outward.

The reflected rays spread out and never meet.

The image looks as though it is behind the mirror.
Life Science Chapter 2 Section 3 Study Guide
Refraction (Pages 57-58)
Key Concept: When light rays enter a medium at an angle, the change in speed causes the rays to ben
or change direction.

As light moves from one medium to the next, it bends. This bending is known as refraction.

Light travels at different speeds in different mediums. For example, light travels more slowly in
water than in air. Therefore, light slows down when it passes from air into water.

When a light wave passes from air into water at an angle, one side of the light wave slows down
before the other side. This causes the light to bend, or refract.

When light rays enter a medium at an angle, the change in speed causes the rays to bed, or
change direction.
Life Science Chapter 2 Section 3 Study Guide
Lenses (Pages 58-60)
Key Concept: An object’s position relative to the focal point determines whether a convex lens forms a
real image or a virtual image. A concave lens can produce only virtual images because parallel light rays
passing through the lens never meet.

A lens is curved piece of glass that is used to bend light.

The type of image formed by a lens depends on the shape of the lens and the position of the
object.

A convex lens is thicker in the center than at the edges. A convex lens bends light rays toward
the center of the lens. All the rays pass through the focal point.

An object’s position relative to the focal point determines whether a convex lens forms a real
image or a virtual image.

A concave lens is thinner in the center than at the edges. A concave lens bends light away from
the center of the lens. The light rays never meet, so the image is always a virtual image. The
image is upright and smaller than the object.

A concave lens can produce only virtual images because parallel light rays passing through the
lens never meet.