Lesson 6 Reflection and Mirrors
Objectives- State the law of reflection; describe how different types of mirrors reflect light
All types of waves, including light, will bounce off an object or be reflected. Reflection is
the bouncing of a wave off of an object. The Law of Reflection says that a wave will
bounce of an object at the same angle it strikes it at.
In the diagram, N is the normal or a line perpendicular to the mirror. The line on
the left or I represents the incoming light wave. It is called the incident. Theta i is the
angle of incidence. The line on the right or R represents the outgoing light wave or
reflected wave. Theta r is called the angle of reflection. According to the law of
reflection, the angle of incidence equals the angle of reflection, or theta i = theta r.
The image produced by a plane flat mirror appears to be as far behind the mirror
as the object is in front of the mirror.
A concave mirror is one whose outer
edges curve towards the center. The light waves
are reflected back to a point in front of the mirror
and create a beam. The place where the beam
meets is called the focal point. The distance from
the center of the mirror to the focal point is called
the focal length.
A convex mirror is one in which the edges
curve away from center of the mirror. These scatter the light outwards and do not form a
beam. The image is distorted and appears to be bigger and farther away than it actually
is.
Questions
What is the law of reflection.
If light strikes a mirror at a 25 degree angle, what angle will it be reflected at?
Define angle of incidence.
Define angle of reflection.
Define focal point.
What happens to the light that is reflected off a concave mirror?
Give an example where a concave mirror is used.
What happens to the light that is reflected off a convex mirror?
Give an example where a convex mirror is used.