Download Reflection of Light

Reflection of Light
Regular Reflection of Light.
• The reflection of light from smooth, shiny
surfaces, such as mirrors, is called regular
reflection.
• Light that travels towards a mirror is called the
incident light.
• Light that is reflected from a mirror is called
the reflected light.
• The study of regular reflection requires
measuring the angles at which the incident
light strikes and the reflected line leaves the
mirror.
• The use of a normal is used to measure the
angles from all mirror surfaces. A normal is
drawn at right angles to the reflecting surface.
• The angle of incidence is the angle between
the incident ray and the normal.
• The angle of reflection is the angle between
the normal and the reflection ray.
Two Laws of Reflection
• The Light Ray Model can be used to explain
how light reflects from a smooth, flat surface.
• The First Law of Reflection states that the
angle of incidence equals the angle of
reflection.
• The Second Law of Reflection states that the
incident ray, the refection ray and the normal
are all on the same plane.
Clear vs. Diffuse Reflection
Smooth, shiny surfaces
have a clear reflection:
Rough, dull surfaces have
a diffuse reflection.
Diffuse reflection is when
light is scattered in
different directions
Diffuse Reflection
• Most objects that reflect light have rough, dull
surfaces. What happens when parallel rays of
light strike a rough surface?
• Because the surface is not smooth, the light
rays are scattered in many directions. This is
called diffuse reflection.
• The laws of reflection still apply to rough
surfaces!
Plane Mirrors
• Most objects that you can see are nonluminous (you can see them because they
reflect light to your eyes).
• Most non-luminous objects have rough
surfaces and will reflect light in a manner that
reveals their shape, colour, and texture.
• Some non-luminous objects reflect light is
such a way that an image is formed. These are
called mirrors.
• Polished metal and calm water are also mirrors.
• A flat reflecting surface is called a plane.
• Plane means two dimensional surface, just like
in math!
Characteristics of Images
(used to study and compare images)
Characteristic
Possible Description
Size
•Smaller than the object viewed
•Larger than the object viewed
•Same size as the object viewed
Attitude
•Upright (right side up)
•Inverted (upside down)
Location
•Appears closer to the plane than the object
•Appears further to the plane than the object
•Appears to be on the opposite side of the plane than the
object
Type
•Real image (can be placed onto a screen)
•Virtual image (can only be seen by looking through an optical
device)
The image of an object reflected by a plane mirror appears
to be at the same distance behind the mirror’s surface as
the object is itself in front.
Drawing Images formed by a Plane
Mirror
1. Draw a line representing the mirror and
shade one side of it. The shade represents
the reflective coating of the mirror. Draw the
object in front of the mirror.
2. Draw the normals from the mirror surface to
significant points, such as the top and bottom
of the object. The number of other points
depends on the object.
3. Measure the length of each normal drawn
from the mirror to the object. Extend the
normal an equal length behind the mirror
surface. Complete the image by connecting
the ends of the normals behind the mirror.
Application of a Plane Mirror
• A Periscope!
• It is an instrument in which plane mirrors are used to
fold light so that the image of an object can be brought
down to a lower level.
• It is used for observing enemy movements from
trenches without any danger of being seen. Sailors on
submarines use periscopes to see things above the
water level.