Chapter 13
Light
Objectives :
• To state the Law of reflection of light
• To describe the characteristics of image
formed by a plane mirror
• To differentiate between a real image and a
virtual image
• To use ray diagram to draw the image formed
by a plane mirror
Terms used with Reflection
• The normal is a line
perpendicular to the
reflecting surface
– It is drawn at the point
where the incident ray
strikes the surface
• The incident ray makes
an angle of i, with the
normal called angle of
incidence.
• The reflected ray makes
an angle of r, with the
normal called the angle
of reflection.
Law of Reflection
The angle of reflection is
equal to the angle of
incidence
i = r
rr
i
PLANE / FLAT MIRRORS
Mirrors form images by reflection of
light waves
Image formed by a plane
mirror is :
- Upright
- Same size as the object
- Laterally inverted
- Same distance behind the
mirror as the object is in front
of the mirror
object distance = image distance
- virtual
Left-Right
Reversal
Why is it painted backwards ?
Examples of images in plane mirrors
Try it yourself !
• How would your name look in a plane mirror ?
DIFFERENCE BETWEEN
REAL AND VIRTUAL
IMAGES
The images which are formed by rays of light that appear to
intersect but which in truth do not exist are called virtual
images. Virtual images cannot be obtained on physical
surfaces.
Real images are formed when rays of light actually intersect
at a single point. Real images can be obtained on physical
surfaces.
Drawing image formed by a plane
mirror