PPT: Ray Optics - 1

# Ray Optics - 1 PPT Physics Class 12

``` Page 1

RAY OPTICS - I
1. Refraction of Light
2. Laws of Refraction
3. Principle of Reversibility of Light
4. Refraction through a Parallel Slab
5. Refraction through a Compound Slab
6. Apparent Depth of a Liquid
7. Total Internal Reflection
8. Refraction at Spherical Surfaces - Introduction
9. Assumptions and Sign Conventions
10.Refraction at Convex and Concave Surfaces
11.Lens Maker’s Formula
12.First and Second Principal Focus
13.Thin Lens Equation (Gaussian Form)
14.Linear Magnification
Page 2

RAY OPTICS - I
1. Refraction of Light
2. Laws of Refraction
3. Principle of Reversibility of Light
4. Refraction through a Parallel Slab
5. Refraction through a Compound Slab
6. Apparent Depth of a Liquid
7. Total Internal Reflection
8. Refraction at Spherical Surfaces - Introduction
9. Assumptions and Sign Conventions
10.Refraction at Convex and Concave Surfaces
11.Lens Maker’s Formula
12.First and Second Principal Focus
13.Thin Lens Equation (Gaussian Form)
14.Linear Magnification
Refraction of Light:
Refraction is the phenomenon of change in the path of light as it travels
from one medium to another (when the ray of light is incident obliquely).
It can also be defined as the phenomenon of change in speed of light
from one medium to another.
Rarer
Rarer
Denser
N
N
r
i
r
i
Laws of Refraction:
I Law: The incident ray, the normal to
the refracting surface at the point of
incidence and the refracted ray all lie in
the same plane.
II Law: For a given pair of media and for
light of a given wavelength, the ratio of
the sine of the angle of incidence to the
sine of the angle of refraction is a
constant. (Snell’s Law)
µ =
sin i
sin r
(The constant µ is called refractive index of the medium,
i is the angle of incidence and r is the angle of refraction.)
µ
Page 3

RAY OPTICS - I
1. Refraction of Light
2. Laws of Refraction
3. Principle of Reversibility of Light
4. Refraction through a Parallel Slab
5. Refraction through a Compound Slab
6. Apparent Depth of a Liquid
7. Total Internal Reflection
8. Refraction at Spherical Surfaces - Introduction
9. Assumptions and Sign Conventions
10.Refraction at Convex and Concave Surfaces
11.Lens Maker’s Formula
12.First and Second Principal Focus
13.Thin Lens Equation (Gaussian Form)
14.Linear Magnification
Refraction of Light:
Refraction is the phenomenon of change in the path of light as it travels
from one medium to another (when the ray of light is incident obliquely).
It can also be defined as the phenomenon of change in speed of light
from one medium to another.
Rarer
Rarer
Denser
N
N
r
i
r
i
Laws of Refraction:
I Law: The incident ray, the normal to
the refracting surface at the point of
incidence and the refracted ray all lie in
the same plane.
II Law: For a given pair of media and for
light of a given wavelength, the ratio of
the sine of the angle of incidence to the
sine of the angle of refraction is a
constant. (Snell’s Law)
µ =
sin i
sin r
(The constant µ is called refractive index of the medium,
i is the angle of incidence and r is the angle of refraction.)
µ
TIPS:
1. µ of optically rarer medium is lower and that of a denser medium is higher.
2. µ of denser medium w.r.t. rarer medium is more than 1 and that of rarer
medium w.r.t. denser medium is less than 1. (µ
air
= µ
vacuum
= 1)
3. In refraction, the velocity and wavelength of light change.
4. In refraction, the frequency and phase of light do not change.
5.
a
µ
m
= c
a
/ c
m
and
a
µ
m
= ?
a
/ ?
m
Principle of Reversibility of Light:
Rarer
(a)
N
r
i
Denser
(b)
sin i
a
µ
b
=
sin r
sin r
b
µ
a
=
sin i
a
µ
b
x
b
µ
a
= 1 or
a
µ
b
= 1 /
b
µ
a
If a ray of light, after suffering any number of
reflections and/or refractions has its path
reversed at any stage, it travels back to the
source along the same path in the opposite
direction.
A natural consequence of the principle of reversibility is that the image and object
positions can be interchanged.  These positions are called conjugate positions.
µ
Page 4

RAY OPTICS - I
1. Refraction of Light
2. Laws of Refraction
3. Principle of Reversibility of Light
4. Refraction through a Parallel Slab
5. Refraction through a Compound Slab
6. Apparent Depth of a Liquid
7. Total Internal Reflection
8. Refraction at Spherical Surfaces - Introduction
9. Assumptions and Sign Conventions
10.Refraction at Convex and Concave Surfaces
11.Lens Maker’s Formula
12.First and Second Principal Focus
13.Thin Lens Equation (Gaussian Form)
14.Linear Magnification
Refraction of Light:
Refraction is the phenomenon of change in the path of light as it travels
from one medium to another (when the ray of light is incident obliquely).
It can also be defined as the phenomenon of change in speed of light
from one medium to another.
Rarer
Rarer
Denser
N
N
r
i
r
i
Laws of Refraction:
I Law: The incident ray, the normal to
the refracting surface at the point of
incidence and the refracted ray all lie in
the same plane.
II Law: For a given pair of media and for
light of a given wavelength, the ratio of
the sine of the angle of incidence to the
sine of the angle of refraction is a
constant. (Snell’s Law)
µ =
sin i
sin r
(The constant µ is called refractive index of the medium,
i is the angle of incidence and r is the angle of refraction.)
µ
TIPS:
1. µ of optically rarer medium is lower and that of a denser medium is higher.
2. µ of denser medium w.r.t. rarer medium is more than 1 and that of rarer
medium w.r.t. denser medium is less than 1. (µ
air
= µ
vacuum
= 1)
3. In refraction, the velocity and wavelength of light change.
4. In refraction, the frequency and phase of light do not change.
5.
a
µ
m
= c
a
/ c
m
and
a
µ
m
= ?
a
/ ?
m
Principle of Reversibility of Light:
Rarer
(a)
N
r
i
Denser
(b)
sin i
a
µ
b
=
sin r
sin r
b
µ
a
=
sin i
a
µ
b
x
b
µ
a
= 1 or
a
µ
b
= 1 /
b
µ
a
If a ray of light, after suffering any number of
reflections and/or refractions has its path
reversed at any stage, it travels back to the
source along the same path in the opposite
direction.
A natural consequence of the principle of reversibility is that the image and object
positions can be interchanged.  These positions are called conjugate positions.
µ
Refraction through a Parallel Slab:
Rarer (a)
Rarer (a)
Denser
(b)
N
N
r
1
i
1
i
2
r
2
M
t
d
y
sin i
1
a
µ
b
=
sin r
1
sin i
2
b
µ
a
=
sin r
2
But
a
µ
b
x
b
µ
a
= 1
sin i
1
sin r
1
sin i
2
sin r
2
x
= 1
It implies that i
1
= r
2
and i
2
= r
1
since i
1
? r
1
and i
2
? r
2
.
Lateral Shift:
t sin d
y =
cos r
1
t sin(i
1
- r
1
)
y =
cos r
1
or
Special Case:
If i
1
is very small, then r
1
is also very small.
i.e. sin(i
1
– r
1
) = i
1
– r
1
and cos r
1
= 1
y = t (i
1
– r
1
)
or
y = t i
1
(1 – 1 /
a
µ
b
)
µ
Page 5

RAY OPTICS - I
1. Refraction of Light
2. Laws of Refraction
3. Principle of Reversibility of Light
4. Refraction through a Parallel Slab
5. Refraction through a Compound Slab
6. Apparent Depth of a Liquid
7. Total Internal Reflection
8. Refraction at Spherical Surfaces - Introduction
9. Assumptions and Sign Conventions
10.Refraction at Convex and Concave Surfaces
11.Lens Maker’s Formula
12.First and Second Principal Focus
13.Thin Lens Equation (Gaussian Form)
14.Linear Magnification
Refraction of Light:
Refraction is the phenomenon of change in the path of light as it travels
from one medium to another (when the ray of light is incident obliquely).
It can also be defined as the phenomenon of change in speed of light
from one medium to another.
Rarer
Rarer
Denser
N
N
r
i
r
i
Laws of Refraction:
I Law: The incident ray, the normal to
the refracting surface at the point of
incidence and the refracted ray all lie in
the same plane.
II Law: For a given pair of media and for
light of a given wavelength, the ratio of
the sine of the angle of incidence to the
sine of the angle of refraction is a
constant. (Snell’s Law)
µ =
sin i
sin r
(The constant µ is called refractive index of the medium,
i is the angle of incidence and r is the angle of refraction.)
µ
TIPS:
1. µ of optically rarer medium is lower and that of a denser medium is higher.
2. µ of denser medium w.r.t. rarer medium is more than 1 and that of rarer
medium w.r.t. denser medium is less than 1. (µ
air
= µ
vacuum
= 1)
3. In refraction, the velocity and wavelength of light change.
4. In refraction, the frequency and phase of light do not change.
5.
a
µ
m
= c
a
/ c
m
and
a
µ
m
= ?
a
/ ?
m
Principle of Reversibility of Light:
Rarer
(a)
N
r
i
Denser
(b)
sin i
a
µ
b
=
sin r
sin r
b
µ
a
=
sin i
a
µ
b
x
b
µ
a
= 1 or
a
µ
b
= 1 /
b
µ
a
If a ray of light, after suffering any number of
reflections and/or refractions has its path
reversed at any stage, it travels back to the
source along the same path in the opposite
direction.
A natural consequence of the principle of reversibility is that the image and object
positions can be interchanged.  These positions are called conjugate positions.
µ
Refraction through a Parallel Slab:
Rarer (a)
Rarer (a)
Denser
(b)
N
N
r
1
i
1
i
2
r
2
M
t
d
y
sin i
1
a
µ
b
=
sin r
1
sin i
2
b
µ
a
=
sin r
2
But
a
µ
b
x
b
µ
a
= 1
sin i
1
sin r
1
sin i
2
sin r
2
x
= 1
It implies that i
1
= r
2
and i
2
= r
1
since i
1
? r
1
and i
2
? r
2
.
Lateral Shift:
t sin d
y =
cos r
1
t sin(i
1
- r
1
)
y =
cos r
1
or
Special Case:
If i
1
is very small, then r
1
is also very small.
i.e. sin(i
1
– r
1
) = i
1
– r
1
and cos r
1
= 1
y = t (i
1
– r
1
)
or
y = t i
1
(1 – 1 /
a
µ
b
)
µ
Refraction through a Compound Slab:
Rarer (a)
Rarer (a)
Denser
(b)
N
N
µ
b
r
1
i
1
r
1
r
2
r
2
i
1
Denser
(c)
µ
c
N
sin i
1
a
µ
b
=
sin r
1
sin r
1
b
µ
c
=
sin r
2
a
µ
b
x
b
µ
c
x
c
µ
a
= 1
sin r
2
c
µ
a
=
sin i
1
a
µ
b
x
b
µ
c
=
a
µ
c
or
b
µ
c
=
a
µ
c
/
a
µ
b
or
µ
a
µ
c
> µ
b
```

## Physics Class 12

105 videos|425 docs|114 tests

## FAQs on Ray Optics - 1 PPT Physics Class 12

 1. What is ray optics?
Ans. Ray optics, also known as geometric optics, is a branch of optics that describes the behavior of light using rays. It focuses on the path of light as it travels through transparent media, such as lenses and mirrors, without considering the wave nature of light.
 2. How does refraction occur in ray optics?
Ans. Refraction occurs in ray optics when light passes from one medium to another with a different refractive index. The change in speed of light causes the ray to bend at the interface between the two media. This bending is known as refraction.
 3. What is the law of reflection in ray optics?
Ans. The law of reflection in ray optics states that the angle of incidence is equal to the angle of reflection. In other words, when a light ray reflects off a smooth surface, the angle between the incident ray and the normal to the surface is equal to the angle between the reflected ray and the normal.
 4. How does a lens work in ray optics?
Ans. A lens in ray optics works by refracting light rays to converge or diverge them. Convex lenses, also known as converging lenses, converge light rays to a focal point. Concave lenses, on the other hand, diverge light rays and create virtual images.
 5. What is the difference between a real image and a virtual image in ray optics?
Ans. In ray optics, a real image is formed when light rays actually converge at a point after passing through a lens or reflecting off a mirror. Real images can be projected onto a screen and are formed when the object is placed beyond the focal point of a lens or mirror. On the other hand, a virtual image is formed when light rays appear to diverge from a point after passing through a lens or reflecting off a mirror. Virtual images cannot be projected onto a screen and are formed when the object is placed within the focal point of a lens or mirror.

## Physics Class 12

105 videos|425 docs|114 tests

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