APPLIED PHYSICS II
Module 2
CO2- Compute the power of lens
M2.01 – Explain basic laws of optics and establish the image formation in
case of convex lens
Optics
Optics is a branch of physics which deals with the study of light.
Optics is classified into ray optics and wave optics.
Reflection
The phenomenon due to which a ray of light, travelling from one optical medium to
another optical medium, bounces off from its surface with a change in angle is called
reflection of light.
Reflection of light is classified into Regular reflection and Irregular reflection.
When a parallel beam of light striking on some smooth and polished surface is
reflected as a parallel beam of light, it is called regular reflection.
E.g.: Reflection takes place from mirrors, polished metals, etc.
When a parallel beam of light striking on some rough surface is reflected in different
directions it is called Irregular reflection or diffused reflection.
E.g.: Reflection from walls, trees, etc.
The angle between the incident ray and normal is called the angle of incidence (i)
The angle between the reflected ray and normal is called the angle of reflection (r).
Laws of Reflection
The incident ray, the reflected ray, and the normal to the surface lie in the same plane
at the point of incidence.
The angle of incidence (i) is always equal to the angle of reflection (r).
Refractive index
Refractive index of a medium (n) is defined as the ratio of the speed of light in
vacuum (c) to the speed of the light in the medium (v).
Medium of high refractive index is called a denser medium.
Medium of low refractive index is called a rarer medium.
, The refractive index of Air (Vacuum) is 1, water is 1.33 and glass is 1.50.
Refraction of Light
The phenomenon of bending of light when it travels from one medium to another is
known as refraction.
When light travels from a rarer medium to a denser medium, light bends towards the
normal at the point of incidence.
When light travels from a denser medium to a rarer medium, light bends away from
the normal.
The angle between the incident ray and the normal is known as angle of incidence (i)
The angle between the refracted ray and the normal is known as angle of refraction
(r).
The angle between the actual path of the ray and the refracted ray is called the angle
of deviation (d).
Laws of Refraction
The incident ray, the refracted ray, and the normal at the point of incidence lies on the
same plane.
Snell’s Law
The ratio of the sine of angle of incidence (i) to the sine of the angle of refraction (r)
is a constant. The constant is equal to the ratio of refractive index of the second
medium ( ) to the refractive index of the first medium( ).
()
( )
Some practical examples of refraction
1) Twinkling of stars
Twinkling of stars is due to the dynamic refraction of light from the star at different
layers of the earth’s atmosphere.
2) Apparent shift in the position of the sun at sunrise and sunset.
Module 2
CO2- Compute the power of lens
M2.01 – Explain basic laws of optics and establish the image formation in
case of convex lens
Optics
Optics is a branch of physics which deals with the study of light.
Optics is classified into ray optics and wave optics.
Reflection
The phenomenon due to which a ray of light, travelling from one optical medium to
another optical medium, bounces off from its surface with a change in angle is called
reflection of light.
Reflection of light is classified into Regular reflection and Irregular reflection.
When a parallel beam of light striking on some smooth and polished surface is
reflected as a parallel beam of light, it is called regular reflection.
E.g.: Reflection takes place from mirrors, polished metals, etc.
When a parallel beam of light striking on some rough surface is reflected in different
directions it is called Irregular reflection or diffused reflection.
E.g.: Reflection from walls, trees, etc.
The angle between the incident ray and normal is called the angle of incidence (i)
The angle between the reflected ray and normal is called the angle of reflection (r).
Laws of Reflection
The incident ray, the reflected ray, and the normal to the surface lie in the same plane
at the point of incidence.
The angle of incidence (i) is always equal to the angle of reflection (r).
Refractive index
Refractive index of a medium (n) is defined as the ratio of the speed of light in
vacuum (c) to the speed of the light in the medium (v).
Medium of high refractive index is called a denser medium.
Medium of low refractive index is called a rarer medium.
, The refractive index of Air (Vacuum) is 1, water is 1.33 and glass is 1.50.
Refraction of Light
The phenomenon of bending of light when it travels from one medium to another is
known as refraction.
When light travels from a rarer medium to a denser medium, light bends towards the
normal at the point of incidence.
When light travels from a denser medium to a rarer medium, light bends away from
the normal.
The angle between the incident ray and the normal is known as angle of incidence (i)
The angle between the refracted ray and the normal is known as angle of refraction
(r).
The angle between the actual path of the ray and the refracted ray is called the angle
of deviation (d).
Laws of Refraction
The incident ray, the refracted ray, and the normal at the point of incidence lies on the
same plane.
Snell’s Law
The ratio of the sine of angle of incidence (i) to the sine of the angle of refraction (r)
is a constant. The constant is equal to the ratio of refractive index of the second
medium ( ) to the refractive index of the first medium( ).
()
( )
Some practical examples of refraction
1) Twinkling of stars
Twinkling of stars is due to the dynamic refraction of light from the star at different
layers of the earth’s atmosphere.
2) Apparent shift in the position of the sun at sunrise and sunset.
