3. The Law of Reflection
• Law of Reflection-When a light ray
strikes a surface and is reflected
• Normal-Imaginary line that is drawn
perpendicular to the surface where the light
ray strikes.
4. The Law of Reflection
• The incident ray and the normal form an
angle called the angle of incidence.
• The reflected
light ray forms
an angle with
the normal
called the angle
of reflection.
5. The Law of Reflection
• law of reflection states that the angle of
incidence is equal to the angle of reflection.
6. Smooth Surface Reflection
• uneven reflection of light
waves from a rough surface
• Causes light waves to reflect
in all directions
Rough Surface Reflection
• Even/parallel reflection of
light waves from and even
surface
Reflection from Surfaces—
RegularVS Diffuse Reflection
7. ConcaveVS Convex Mirrors
Convex Mirror
• has a surface that curves
outward, like the back of a
spoon
• Convex mirrors cause light
waves to spread out, or
diverge.
Concave Mirror
• a surface that is curved
inward, like the bowl of a
spoon.
• Unlike plane mirrors, concave
mirrors cause light rays to
come together, or converge
8. Scattering of Light
• When diffuse reflection occurs, light waves
that were traveling in a single direction are
reflected, and then travel in many different
directions.
• This is known as scattering.
• Scattering also can occur when light waves
strike small particles, such as dust.
9. Reflection by Plane Mirrors
• These light rays
bounce off the
person according to
the law of reflection,
and some of them
strike the mirror.
Reflection and Mirrors
2
• Light waves from the Sun or another source
of light strike each
part of the person.
10. Reflection by Plane Mirrors
Reflection and Mirrors
2
• The rays that strike
the mirror also are
reflected according
to the law of
reflection.
11. The Image in a Plane Mirror
• Although the light rays bounced off the
mirror’s surface, your brain interprets
them as having followed straight lines.
• This makes the
reflected light
rays look as if
they are coming
from behind the
mirror.
Reflection and Mirrors
2
12. 2a) Reflection of light :-
When light falls on a highly polished surface like a mirror most of
the light is sent back into the same medium. This process is called
reflection of light.
a) Laws of reflection of light :-
i) The angle of incidence is equal to the angle of reflection.
ii) The incident ray, the reflected ray and the normal to the mirror at
the point of incidence all lie in the same plane.
13. i) The image is erect.
ii) The image is same size as the object.
iii) The image is at the same distance from the mirror as the object is in
front of it.
iv) The image is virtual (cannot be obtained on a screen).
v) The image is laterally inverted.
14. 3) Spherical mirrors :-
Spherical mirror is a curved mirror which is a part of a hollow
sphere. Spherical mirrors are of two types. They are concave mirror
and convex mirror.
i) Concave mirror :- is a spherical mirror whose reflecting surface is
curved inwards. Rays of light parallel to the principal axis after
reflection from a concave mirror meet at a point (converge) on the
principal axis.
ii) Convex mirror :- is a spherical mirror whose reflecting surface is
curved inwards. Rays of light parallel to the principal axis after
reflection from a convex mirror get diverged and appear to come from a
point behind the mirror.
F
F
15. 4) Terms used in the study of spherical mirrors :-
i) Center of curvature :- is the centre of the sphere of which the mirror
is a part (C).
ii) Radius of curvature :- is the radius of the sphere of which the mirror
is a part (CP).
iii) Pole :- is the centre of the spherical mirror (P).
iv) Principal axis :- is the straight line passing through the centre of
curvature and the pole (X-Y).
v) Principal focus :-
In a concave mirror, rays of light parallel to the principal axis after
reflection meet at a point on the principal axis called principal
focus(F).
In a convex mirror, rays of light parallel to the principal axis after
reflection get diverged and appear to come from a point on the
principal axis behind the mirror called principal focus (F).
vi) Focal length :- is the distance between the pole and principal focus
(f). In a spherical mirror the radius of curvature is twice the focal
length.
R = 2f or f = R
2
16. X C F P Y
C – centre of curvature CP – radius of curvature
P – pole XY – principal axis
F – principal focus PF – focal length
17. 5) Reflection by spherical mirrors :-
i) In a concave mirror a ray of light parallel to the principal
axis after reflection passes through the focus.
In a convex mirror a ray of light parallel to the principal
axis after reflection appears to diverge from the focus.
C F P P F C
18. ii) In a concave mirror a ray of light passing through the
focus after reflection goes parallel to the principal axis.
In a convex mirror a ray of light directed towards the
focus after reflection goes parallel to the principal axis.
C F P P F C
19. iii) In a concave mirror a ray of light passing through the
centre of curvature after reflection is reflected back along
the same direction.
In a convex mirror a ray of light directed towards the
centre of curvature after reflection is reflected back along
the same direction.
C F P P F C
20. iv) In a concave or a convex mirror a ray of light directed
obliquely at the pole is reflected obliquely making equal
angles with the principal axis.
C F i P i P F C
r r
21.
22. Concave Mirrors
• A straight line drawn perpendicular to the
center of a concave or convex mirror is
called the optical axis.
• Light rays that travel parallel to the optical
axis and strike the mirror are reflected so
that they pass through a single point of the
optical axis called the focal point.
Reflection and Mirrors
2
• The distance along the optical axis from the
center of the mirror to the focal point is
called the focal length.
23. Concave Mirrors
• If the object is farther from the mirror than
the focal point, the image appears to be
upside down, or inverted.
• The size of the image decreases as the object
is moved farther away from the mirror.
Reflection and Mirrors
2
• If the object is closer to the mirror than
one focal length, the image is upright and
gets smaller as the object moves closer to
the mirror.
24. Concave Mirrors
• A concave mirror can
produce a focused beam of
light if a source of light is
placed at the mirror’s focal
point.
• Flashlights and automobile
headlights use concave
mirrors to produce directed
beams of light.
Reflection and Mirrors
2
25. Convex Mirrors
• A convex mirror causes light rays to spread
apart, or diverge.
Reflection and Mirrors
2
26. Convex Mirrors
Reflection and Mirrors
2
• Like the image formed by a plane mirror, the
image formed by a convex mirror seems to
be behind the mirror. The image always
is upright
and smaller
than the
object.
