The document discusses the laws of reflection and refraction of light. It defines reflection as light bouncing back and describes the law of reflection which states that the angle of incidence equals the angle of reflection. Reflection can be specular from smooth surfaces or diffuse from rough surfaces. Reflection of light rays from spherical mirrors follows specific rules depending on whether the mirror is concave or convex. Refraction is defined as the change in direction of a light ray when passing from one medium to another. Snell's law relates the angles of incidence and refraction, with the ratio of their sines being a constant called the refractive index. Lenses use refraction to form real or virtual images depending on whether the lens is converging or diver

1. Name - Alwin M Reji
Class – X
Roll - 8

2. Reflection :: It is the process of sending back
Reflection It is the process of sending back
the incidents light.
the incidents light.


Law of reflection of light:
Law of reflection of light:
i. The angle of incident is equal to the
i. The angle of incident is equal to the
angle of reflection.
angle of reflection.
ii. The incidence ray, the normal to the
ii. The incidence ray, the normal to the
mirror at the point of incidence and the
mirror at the point of incidence and the
reflected ray, all lie in the same plane.
reflected ray, all lie in the same plane.

3. Reflection from a mirror:
Normal
Reflected ray
Incident ray
Angle of incidence
Mirror
Angle of
reflection

4. Texture affects reflection
Texture affects reflection
Diffuse reflection (rough)
Diffuse reflection (rough)
reflects light in many different directions,
reflects light in many different directions,
Specular reflection (smooth)
Specular reflection (smooth)
reflects light in only one direction
reflects light in only one direction
Smooth – variations in surface < λ
Smooth – variations in surface < λ

6. Light striking a mirror reflects at the same
Light striking a mirror reflects at the same
angle that it struck the mirror
angle that it struck the mirror

8.  These law of reflection are applicable to all type of
 These law of reflection are applicable to all type of
reflecting surfaces including spherical surface.
reflecting surfaces including spherical surface.
 Image formed by a plane mirror is always virtual and
 Image formed by a plane mirror is always virtual and
erect. The size of the image is equal to that of the
erect. The size of the image is equal to that of the
object. The image formed is as far behind the mirror as
object. The image formed is as far behind the mirror as
the object is in front of it. It is laterally inverted, i.e.,
the object is in front of it. It is laterally inverted, i.e.,
the image is inverted sideways
the image is inverted sideways

9. A spherical mirror, whose reflection surface is
A spherical mirror, whose reflection surface is
curved inwards is called a concave mirror and the
curved inwards is called a concave mirror and the
one whose reflecting surface is curved outwards is
one whose reflecting surface is curved outwards is
called a convex mirror.
called a convex mirror.

10. Sign of M
Orientation of Image
Type of Image
+
Upright
Virtual
–
Inverted
Real

11. •• A ray traveling through C will reflect back
A ray traveling through C will reflect back
through C
through C
•• A ray traveling through (f) will reflect parallel to
A ray traveling through (f) will reflect parallel to
the PA
the PA
•• A ray traveling to the intersection of the PA and
A ray traveling to the intersection of the PA and
the mirror will reflect at the same angle below the
the mirror will reflect at the same angle below the
PA.
PA.
•• A ray traveling parallel to PA will reflect through
A ray traveling parallel to PA will reflect through
the focal point
the focal point

13. Hard Surface

14. Reflective surface is on the outside of
Reflective surface is on the outside of
the curve.
the curve.
The points ff and C are located behind
The points and C are located behind
the mirror
the mirror
negative
negative

16. A ray parallel to the PA will reflect directly away
A ray parallel to the PA will reflect directly away
from f.
from f.
A ray towards ff will reflect parallel to the PA
A ray towards will reflect parallel to the PA
A ray towards C will reflect directly away from C.
A ray towards C will reflect directly away from C.
A ray to the intersection of PA and mirror will
A ray to the intersection of PA and mirror will
reflect at the same angle below the OA.
reflect at the same angle below the OA.
Trace the 3 diverging lines back through the mirror
Trace the 3 diverging lines back through the mirror
to reveal the location of the image which is always
to reveal the location of the image which is always
virtual
virtual

17. When a ray of light travels obliquely one medium to
When a ray of light travels obliquely one medium to
another, the direction of propagation of light in the
another, the direction of propagation of light in the
second medium changes. This phenomenon is
second medium changes. This phenomenon is
known as refraction of light.
known as refraction of light.

18. A good analogy for refracting light is a
A good analogy for refracting light is a
lawnmower traveling from the sidewalk
lawnmower traveling from the sidewalk
onto mud
onto mud

19. The speed of light is different in different media.
The speed of light is different in different media.
i.e., refraction is due to change in the speed of light
i.e., refraction is due to change in the speed of light
on going from one medium to another.
on going from one medium to another.

22. 1. The incident ray, the refracted ray and the normal to the
1. The incident ray, the refracted ray and the normal to the
interface to two transparent media at the point of incidence,
interface to two transparent media at the point of incidence,
all lie in the same plane.
all lie in the same plane.
2. The ratio of sine of angle of incidence to the sine of angle
2. The ratio of sine of angle of incidence to the sine of angle
of refraction is a constant, for the light of a given colour
of refraction is a constant, for the light of a given colour
and for the given pair of media. This law is known as
and for the given pair of media. This law is known as
Snell's law of refraction. If the angle of incident and rr is the
Snell's law of refraction. If the angle of incident and is the
angle of refraction then,
angle of refraction then,
This constant value is called the refractive
This constant value is called the refractive
index of the second medium with respect to the first.
index of the second medium with respect to the first.

24. Converging
Diverging
f- curve of lens & index of refraction

25. 1. Ray parallel to PA, refracts through far
1. Ray parallel to PA, refracts through far
focal point
focal point
2. Ray through center of lens, continues
2. Ray through center of lens, continues
straight line
straight line
3. Ray through near focal point, refracts
3. Ray through near focal point, refracts
through lens, continues parallel to PA
through lens, continues parallel to PA
Treat lens as though it were a flat plane.
Treat lens as though it were a flat plane.

27. Diverging Lens Diagram
• Because the rays that enter a diverging lens do not
intersect a virtual image is formed by tracing back
the refracted rays.
• Ray 1 - parallel to PA, refracts away from near f,
trace back to near f.
• Ray 2 - ray toward far f, refracts parallel to PA,
trace back parallel to PA
• Ray 3 - ray through center, continues straight,
trace back toward object

29. Sign
+
–
p
q
Near side of Far side of
lens
lens
Far side of Near side of
lens
lens
F
Converging
Lens
Diverging
Lens

30. p = 30.0cm
p = 30.0cm
ff = 10.cm
= 10.cm

31. p = 12.5cm
p = 12.5cm
ff = -10.0cm
= -10.0cm