OBJECTIVE
• At the end of this lesson, you should be
able to:
– Describe the characteristic of the image
formed by reflection of light.
– Solve problem involving reflection of
light.
WHAT IS MEANT BY LIGHT?
• Light is a form of energy.
• It travels in straight line and high speed
about 3 x 108 ms-1.
• It can be reflected, refracted and
dispersed.
• Rays are the path and direction which light
energy flows.
• When the light rays fall on the surface of an
object, they are either:
– Reflected
• When it hits a smooth surface.
– Refracted
• When it passes through a transparent
object.
– Absorbed
• When it strikes a black or dark body.
REFLECTION OF LIGHT
• Reflection of light occurs when light rays falling
on a surface and bounce off the surface.
• Light striking different surface will be reflected
differently:
– Regular reflection is the reflection of parallel light rays
in a certain direction from a smooth surface such as
plane mirror.
– Diffused reflection is the reflection of parallel light rays
in all directions from a rough surface such as white
paper.
Types of reflection
Regular reflection
Diffused reflection
Why do you see an image in the
mirror?
• Light is reflected off your body as an
image and you are then able to see the
image that is reflected. You will see the
image as if it is inside the mirror! When
light bounces off a surface, it is called
reflection.
TYPE OF MIRROR
• Plane mirror
• Curve mirror
CURVED MIRRORS
•
Is actually a spherical mirror.
•
Has the same shape as a section of a
large sphere.
• Type of curved mirrors:
i.
concave mirrors
ii.
convex mirrors
CONVEX MIRRORS
• Curves outwards.
• Parallel light rays the hit
the convex surface are
reflected outwards.
• Also known as a
diverging mirror.
• Only produce a virtual
image.
CONCAVE MIRRORS
• Curves inward.
• Parallel light rays that
hit the concave
surface are reflected
inwards.
• Also known as a
converging mirror.
CHARACTERISTIC OF THE
IMAGE FORMED IN A PLANE
MIRROR.
•
•
•
•
Upright
Same size as the object
Laterally inverted
Distance between image and mirror same
as distance between object and mirror.
• Virtual - image cannot captured on the
screen.
• Why the word AMBULANCE is written in
reverse letter at in front of the body?
• The word ambulance is written in reverse
letter because the lettering will appear
normal when the viewed through the rearview mirror of car in front of the driver
seat.
PROBLEM SOLVING
PROBLEM
SOLVING
Solution no 1
• Initially, the distance between Jacelyn and her image
=5+5
= 10m
• After Jacelyn and the mirror moved, the distance between
Jacelyn and the mirror
=5+1–3
= 3 m.
• So, distance between Jacelyn and the new position of the
image
=2x3
=6m
• The reduction in distance between Jacelyn and her image
= 10 – 6
=4m#
PROBLEM SOLVING
Solution no 2
•
The distance between Helmi and the plane
mirror
12 /2 = 6 m
•
i) The new distance between Helmi and the
plane mirror
6m – 2m = 4 m
•
ii) The new distance between Helmi and his
image
4m + 4m = 8m
PROBLEM SOLVING
• Answer no 3
= 4m
•What is meant by light?
•Light is a form of energy.
•How it travels?
•It travels in straight line and high speed about 3 x 108 ms-1.
•When the light ray strike on the surface of an object, what
happen to the light ray?
•It can be reflected, refracted and absorbed.
•How the reflection of light occurs?
•Reflection of light occurs when light rays strike on a
surface and bounce off the surface.
•Give me 2 types of reflection?
•Regular reflection
•Diffused reflection
OBJECTIVE
• At the end of this lesson, you should be
able to:
– State the law of reflection of light.
– Solve problem involving reflection of
light.
How does light behave during
reflection?
• How can we investigate?
LAWS OF REFLECTION
1.
•
FIRST LAW state that:
The incident ray, the
reflected ray and the normal
to the surface all lie in the
same plane.
2.
•
SECOND LAW state that:
The angle of incidence, i is
equal to the angle of
reflection, r.

Angle of incident, i is angle
between incident ray and the
normal.
Angle of reflection, r is angle
between reflected ray and
the normal.

Example
PROBLEM SOLVING
Question 1
• Figure 1 show of light ray is directed to a
plane mirror.
Incident ray
30°
Plane mirror
What is the angle of reflection?
Question 2
• Figure 2 show a ray of light reflected on a plane
mirror. The angle between the incident ray and
reflected ray is 100°. The mirror is then turned to
10° in the anticlockwise direction as shown
Incident ray
Reflected ray
100°
10°
• What is the new angle between the incident ray
and the reflected ray?
Answer
• Angle of incident = 90° - 30°
= 60°
• Angle of reflection = Angle of incident
Incident ray
Reflected ray
60°
60°
30°
Answer
• Before the mirror turns, the angle of
incidence is 50°. When the mirror has
turned to an angle of 10° , the normal also
turn to 10° . The new angle of incidence is
now 40° (50° - 10°). Therefore, the angle
between the incident ray and reflected ray
has become 80°