NCERT Solutions, Chapter 10: Light Reflection and Refraction, Class 10 (Science)

# NCERT Solutions, Chapter 10: Light Reflection and Refraction, Class 10 (Science) PDF Download

``` Page 1

Light is a form of energy, which enable us to see the object.
In this chapter we will study the phenomena of reflection and refraction using the
property of light i.e. straight line propagation (Light wave travel from one point to
another, along a straight line).
Reflection of Light
When the light is allowed to fall on highly polished surface, such as mirror, most of
the light gets reflected.
Laws of Reflection
1. The angle of incidence is always equal to
angle of reflection.
Ð i = Ð r
2. The incident ray, reflected ray and the
normal to the reflecting surface at the
point of incidence lie in the same plane.
Image formed by Plane Mirror (Plane reflecting surface)
CHAPTER – 10
LIGHT-REFLECTION
& REFRACTION
Points of incidences
Incident
ray
Reflected
ray
normal
i r
A
B
1
A
1
B
Ð i
Ð r
Plane Mirror
Image Object
1) Virtual (imaginary) & Erect (Virtual Þ The image that do not form on
screen.)
2) Laterally inverted (The left side of object appear on right side of image)
3) The size of image is equal to that of object
X-Science
96
Page 2

Light is a form of energy, which enable us to see the object.
In this chapter we will study the phenomena of reflection and refraction using the
property of light i.e. straight line propagation (Light wave travel from one point to
another, along a straight line).
Reflection of Light
When the light is allowed to fall on highly polished surface, such as mirror, most of
the light gets reflected.
Laws of Reflection
1. The angle of incidence is always equal to
angle of reflection.
Ð i = Ð r
2. The incident ray, reflected ray and the
normal to the reflecting surface at the
point of incidence lie in the same plane.
Image formed by Plane Mirror (Plane reflecting surface)
CHAPTER – 10
LIGHT-REFLECTION
& REFRACTION
Points of incidences
Incident
ray
Reflected
ray
normal
i r
A
B
1
A
1
B
Ð i
Ð r
Plane Mirror
Image Object
1) Virtual (imaginary) & Erect (Virtual Þ The image that do not form on
screen.)
2) Laterally inverted (The left side of object appear on right side of image)
3) The size of image is equal to that of object
X-Science
96
4. The image formed is as for behind the mirror as the object is in front of it.
Reflection of light by spherical Mirrors
Mirrors, whose reflecting surface are curved inward or outward spherically are
called spherical mirror.
For example - Spoon } ® The curved surface of shinning spoon can be considered
as curved mirror.
If it is curved inward ® Act as concave mirror
If it is curved outward ® Act as a convex mirror.
Reflecting
side
Reflecting
side
Concave
Mirror
OR CONVERGING
MIRROR
Convex
mirror
OR DIVERGING
MIRROR
Principal
Axis
R
C F f
focal length
P
Concave
Mirror
R
C f F
focal length
Convex
Mirror
P
Principal
Axis
Few Basic terms related to Spherical Mirror
X-Science
97
Page 3

Light is a form of energy, which enable us to see the object.
In this chapter we will study the phenomena of reflection and refraction using the
property of light i.e. straight line propagation (Light wave travel from one point to
another, along a straight line).
Reflection of Light
When the light is allowed to fall on highly polished surface, such as mirror, most of
the light gets reflected.
Laws of Reflection
1. The angle of incidence is always equal to
angle of reflection.
Ð i = Ð r
2. The incident ray, reflected ray and the
normal to the reflecting surface at the
point of incidence lie in the same plane.
Image formed by Plane Mirror (Plane reflecting surface)
CHAPTER – 10
LIGHT-REFLECTION
& REFRACTION
Points of incidences
Incident
ray
Reflected
ray
normal
i r
A
B
1
A
1
B
Ð i
Ð r
Plane Mirror
Image Object
1) Virtual (imaginary) & Erect (Virtual Þ The image that do not form on
screen.)
2) Laterally inverted (The left side of object appear on right side of image)
3) The size of image is equal to that of object
X-Science
96
4. The image formed is as for behind the mirror as the object is in front of it.
Reflection of light by spherical Mirrors
Mirrors, whose reflecting surface are curved inward or outward spherically are
called spherical mirror.
For example - Spoon } ® The curved surface of shinning spoon can be considered
as curved mirror.
If it is curved inward ® Act as concave mirror
If it is curved outward ® Act as a convex mirror.
Reflecting
side
Reflecting
side
Concave
Mirror
OR CONVERGING
MIRROR
Convex
mirror
OR DIVERGING
MIRROR
Principal
Axis
R
C F f
focal length
P
Concave
Mirror
R
C f F
focal length
Convex
Mirror
P
Principal
Axis
Few Basic terms related to Spherical Mirror
X-Science
97
1. Principal axis : Line joining the pole and centre of curvature of the spherical
mirror.
2. Pole : The geometrical central point of the reflecting spherical surface.
(aperture), denoted by (P).
3. Aperture : The width of reflecting spherical surface.
4. Centre of curvature : The  reflecting surface of a spherical mirror form a part
of sphere. It has a centre, which is known as centre of curvature, denoted by
(C)
5. Radius of curvature : The separation between the pole and the centre of
curvature. ie.  PC = R
6. Focus point : The point on the principal axis, where all parallel rays meet
after reflection, denoted by (F)
7. Focal length : The length between the pole and focus point i.e.  PF = f
8. Relationship between focal length and Radius of curvature.
F =
R
2
Image formation by spherical Mirror
Before we learn the formation of image or ray diagram, let us go through few tips
a) Remember, A say of light which is parallel to principle axis always pass
through focus (meet at focus) or vice-versa
Principal
Axis
C F
CONCA VE
MIRROR
P
CONCA VE
MIRROR
Principal
Axis
C F
P
F C P
Principal
Axis
CONVEX MIRROR
Appear as if coming
from focus pt in case of convex mirror
X-Science
98
Page 4

Light is a form of energy, which enable us to see the object.
In this chapter we will study the phenomena of reflection and refraction using the
property of light i.e. straight line propagation (Light wave travel from one point to
another, along a straight line).
Reflection of Light
When the light is allowed to fall on highly polished surface, such as mirror, most of
the light gets reflected.
Laws of Reflection
1. The angle of incidence is always equal to
angle of reflection.
Ð i = Ð r
2. The incident ray, reflected ray and the
normal to the reflecting surface at the
point of incidence lie in the same plane.
Image formed by Plane Mirror (Plane reflecting surface)
CHAPTER – 10
LIGHT-REFLECTION
& REFRACTION
Points of incidences
Incident
ray
Reflected
ray
normal
i r
A
B
1
A
1
B
Ð i
Ð r
Plane Mirror
Image Object
1) Virtual (imaginary) & Erect (Virtual Þ The image that do not form on
screen.)
2) Laterally inverted (The left side of object appear on right side of image)
3) The size of image is equal to that of object
X-Science
96
4. The image formed is as for behind the mirror as the object is in front of it.
Reflection of light by spherical Mirrors
Mirrors, whose reflecting surface are curved inward or outward spherically are
called spherical mirror.
For example - Spoon } ® The curved surface of shinning spoon can be considered
as curved mirror.
If it is curved inward ® Act as concave mirror
If it is curved outward ® Act as a convex mirror.
Reflecting
side
Reflecting
side
Concave
Mirror
OR CONVERGING
MIRROR
Convex
mirror
OR DIVERGING
MIRROR
Principal
Axis
R
C F f
focal length
P
Concave
Mirror
R
C f F
focal length
Convex
Mirror
P
Principal
Axis
Few Basic terms related to Spherical Mirror
X-Science
97
1. Principal axis : Line joining the pole and centre of curvature of the spherical
mirror.
2. Pole : The geometrical central point of the reflecting spherical surface.
(aperture), denoted by (P).
3. Aperture : The width of reflecting spherical surface.
4. Centre of curvature : The  reflecting surface of a spherical mirror form a part
of sphere. It has a centre, which is known as centre of curvature, denoted by
(C)
5. Radius of curvature : The separation between the pole and the centre of
curvature. ie.  PC = R
6. Focus point : The point on the principal axis, where all parallel rays meet
after reflection, denoted by (F)
7. Focal length : The length between the pole and focus point i.e.  PF = f
8. Relationship between focal length and Radius of curvature.
F =
R
2
Image formation by spherical Mirror
Before we learn the formation of image or ray diagram, let us go through few tips
a) Remember, A say of light which is parallel to principle axis always pass
through focus (meet at focus) or vice-versa
Principal
Axis
C F
CONCA VE
MIRROR
P
CONCA VE
MIRROR
Principal
Axis
C F
P
F C P
Principal
Axis
CONVEX MIRROR
Appear as if coming
from focus pt in case of convex mirror
X-Science
98
Principal
Axis
C F
CONCA VE
MIRROR
Pole (P)
C
F
P
i
r
Ð i = Ð r
b) A ray of light which passes through centre of curvature (it is also known as
normal at the point of incidence on spherical mirror) will retrace their path
after reflection
c) A ray of light falling on pole get reflected at the same angle on the other side of
principal axis.
X-Science
F C P
Principal
Axis
CONVEX
MIRROR
C F
Principal
Axis
P
Ð i = Ð r
Ð i
Ð r
F C
99
Page 5

Light is a form of energy, which enable us to see the object.
In this chapter we will study the phenomena of reflection and refraction using the
property of light i.e. straight line propagation (Light wave travel from one point to
another, along a straight line).
Reflection of Light
When the light is allowed to fall on highly polished surface, such as mirror, most of
the light gets reflected.
Laws of Reflection
1. The angle of incidence is always equal to
angle of reflection.
Ð i = Ð r
2. The incident ray, reflected ray and the
normal to the reflecting surface at the
point of incidence lie in the same plane.
Image formed by Plane Mirror (Plane reflecting surface)
CHAPTER – 10
LIGHT-REFLECTION
& REFRACTION
Points of incidences
Incident
ray
Reflected
ray
normal
i r
A
B
1
A
1
B
Ð i
Ð r
Plane Mirror
Image Object
1) Virtual (imaginary) & Erect (Virtual Þ The image that do not form on
screen.)
2) Laterally inverted (The left side of object appear on right side of image)
3) The size of image is equal to that of object
X-Science
96
4. The image formed is as for behind the mirror as the object is in front of it.
Reflection of light by spherical Mirrors
Mirrors, whose reflecting surface are curved inward or outward spherically are
called spherical mirror.
For example - Spoon } ® The curved surface of shinning spoon can be considered
as curved mirror.
If it is curved inward ® Act as concave mirror
If it is curved outward ® Act as a convex mirror.
Reflecting
side
Reflecting
side
Concave
Mirror
OR CONVERGING
MIRROR
Convex
mirror
OR DIVERGING
MIRROR
Principal
Axis
R
C F f
focal length
P
Concave
Mirror
R
C f F
focal length
Convex
Mirror
P
Principal
Axis
Few Basic terms related to Spherical Mirror
X-Science
97
1. Principal axis : Line joining the pole and centre of curvature of the spherical
mirror.
2. Pole : The geometrical central point of the reflecting spherical surface.
(aperture), denoted by (P).
3. Aperture : The width of reflecting spherical surface.
4. Centre of curvature : The  reflecting surface of a spherical mirror form a part
of sphere. It has a centre, which is known as centre of curvature, denoted by
(C)
5. Radius of curvature : The separation between the pole and the centre of
curvature. ie.  PC = R
6. Focus point : The point on the principal axis, where all parallel rays meet
after reflection, denoted by (F)
7. Focal length : The length between the pole and focus point i.e.  PF = f
8. Relationship between focal length and Radius of curvature.
F =
R
2
Image formation by spherical Mirror
Before we learn the formation of image or ray diagram, let us go through few tips
a) Remember, A say of light which is parallel to principle axis always pass
through focus (meet at focus) or vice-versa
Principal
Axis
C F
CONCA VE
MIRROR
P
CONCA VE
MIRROR
Principal
Axis
C F
P
F C P
Principal
Axis
CONVEX MIRROR
Appear as if coming
from focus pt in case of convex mirror
X-Science
98
Principal
Axis
C F
CONCA VE
MIRROR
Pole (P)
C
F
P
i
r
Ð i = Ð r
b) A ray of light which passes through centre of curvature (it is also known as
normal at the point of incidence on spherical mirror) will retrace their path
after reflection
c) A ray of light falling on pole get reflected at the same angle on the other side of
principal axis.
X-Science
F C P
Principal
Axis
CONVEX
MIRROR
C F
Principal
Axis
P
Ð i = Ð r
Ð i
Ð r
F C
99
F
C
r
i
P
(passing
through c)
normal
at pt of incidence
P
C F
C
1
B
1
A
B
A
F
P
object
image
Ð r
Ð i
A
P
A
B
1
B
F
Note : A ray of light passes through centre of cus-valerie  reflecting spherical
surface is always act as normal at the point of incidence. If we know the normal we
can draw angle of incidence and angle of reflection
Note : The image will only form when two or more rays meets at apoint. Image
formation by a concave mirror for different position of the object
1. Object
At infinity
Position of
Image
At focus
Size of
Image
Highly diminished
(point size)
Nature
Real and
Inverted
2. Object
Beyond C
Position of
Image
Between F&C
Size of
Image
Small
Nature
Real and
Inverted
3. Object
At C
Position of
Image
At C
Size of
Image
Same Size
of object
Nature
Real and
Inverted
X-Science
F C P
Ð i
Ð r
100
```

## FAQs on NCERT Solutions, Chapter 10: Light Reflection and Refraction, Class 10 (Science)

 1. What is the difference between reflection and refraction?
Ans. Reflection is the bouncing back of light when it strikes a smooth and shiny surface, whereas refraction is the bending of light as it passes from one medium to another.
 2. How does light travel in a straight line?
Ans. Light travels in a straight line because it follows the law of rectilinear propagation. According to this law, light travels in a straight line until it encounters an obstacle or a medium of different optical density.
 3. Why does a pencil appear bent when placed in a glass of water?
Ans. When a pencil is placed in a glass of water, the light rays coming from the pencil bend when they enter the water due to refraction. This bending of light makes the pencil appear bent.
 4. What is the angle of incidence?
Ans. The angle of incidence is the angle formed between an incident ray and the normal to the surface at the point of incidence. It is denoted by the symbol 'i'.
 5. Why does a mirror reflect light?
Ans. A mirror reflects light due to the property of reflection. When light falls on a smooth and shiny surface, such as a mirror, it undergoes reflection and bounces back in a predictable manner, allowing us to see our own image or any other object in the mirror.
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