Engineering Physics
(For B.Tech 1st & 2nd SEM)
By
Prahalad ‘Holiwala’
UNIT-1ST (WAVE OPTICS)
Michelson Fraunhofer
Prahalad ‘Holiwala’ () 1
, UNIT – 1st (Wave Optics)
Topics:-
(1). Interference of Light
1.(a). Newton’s Ring Experiment
1.(b). Michelson’s Interferometer
(2). Diffraction of Light
2.(a). Fraunhofer Diffraction due to single slit
2.(b). Plane Transmission Grating
(3). Resolving Power
3.(a). Resolving Power of Grating
(4). XRD (X-ray Diffraction)
4.(a). Bragg’s Law
Prahalad ‘Holiwala’ () 2
, (1).INTEREFERENCE OF LIGHT:-
When two or more light waves with same wavelength (frequency) and almost same
amplitude are travelling in same direction and superimpose at a single point then produce the
interference pattern in the form of black and white fringes. This phenomenon is known as the
interference of light. In another words the interference of light is redistribution of energy in
the terms of black & white fringes.
Conditions of interference of light:- The light waves must be satisfied the following
conditions for the interference.
(1). The two or more light waves are required for interference.
(2). All light waves should be travelled in same direction.
(3). All light waves should have same wavelength and almost same amplitude.
(4). All light waves should be superimposed at a single point.
Types of interference:- There are two types of interference of light.
(1). Constructive interference:- According to the Young’s theory, when the path difference
between the light waves is nλ then produce the constructive interference or bright fringe.
(2). Destructive interference:- According to the Young’s theory, when the path difference
between the light waves is (2n±1)λ/2 then produce the destructive interference or dark fringe.
1.(a).NEWTON’S RING
INTRODUCTION :-
When a Plano convex lens of large radius of curvature is placed with its convex
surface in contact with glass plate, then a thin air film is formed between the large surface of
the lens and the upper surface of the plate. At the point of contact the air film is zero.
When the monochromatic light is allowed to fall normally on this film then a system of
alternate bright and dark rings concentric rings are observed with centre at the point of
contact of lens and plate. Each fringe is formed on the locus of points of equal thickness,
which is a circle with point of contact as centre. Such circular rings were first produced by
Newton, so they are known as Newton’s Rings.
EXPERIMENTAL ARRANGEMENT :-
Prahalad ‘Holiwala’ () 3
, In this experiment, S is a monochromatic source (Sodium light source) of light at the
focus of lens L, so a horizontal parallel beam of light falls on the glass plate P, which is
inclined at 450 to the incident beam. The inclined glass plate P reflects a part of incident light
towards the air film enclosed by the plano-convex lens and glass plate. The reflected light
from the upper surface and lower surface of the air thin film is interfere to each other and
produce the interference pattern in the form of circular dark and bright fringes. These circular
fringes are observed by the microscope.
Working:-
When a light ray AB falls normally on a plano-convex lens, light rays BR1 and CR2
reflected back from the top and bottom surface of the air thin film.
Prahalad ‘Holiwala’ () 4
(For B.Tech 1st & 2nd SEM)
By
Prahalad ‘Holiwala’
UNIT-1ST (WAVE OPTICS)
Michelson Fraunhofer
Prahalad ‘Holiwala’ () 1
, UNIT – 1st (Wave Optics)
Topics:-
(1). Interference of Light
1.(a). Newton’s Ring Experiment
1.(b). Michelson’s Interferometer
(2). Diffraction of Light
2.(a). Fraunhofer Diffraction due to single slit
2.(b). Plane Transmission Grating
(3). Resolving Power
3.(a). Resolving Power of Grating
(4). XRD (X-ray Diffraction)
4.(a). Bragg’s Law
Prahalad ‘Holiwala’ () 2
, (1).INTEREFERENCE OF LIGHT:-
When two or more light waves with same wavelength (frequency) and almost same
amplitude are travelling in same direction and superimpose at a single point then produce the
interference pattern in the form of black and white fringes. This phenomenon is known as the
interference of light. In another words the interference of light is redistribution of energy in
the terms of black & white fringes.
Conditions of interference of light:- The light waves must be satisfied the following
conditions for the interference.
(1). The two or more light waves are required for interference.
(2). All light waves should be travelled in same direction.
(3). All light waves should have same wavelength and almost same amplitude.
(4). All light waves should be superimposed at a single point.
Types of interference:- There are two types of interference of light.
(1). Constructive interference:- According to the Young’s theory, when the path difference
between the light waves is nλ then produce the constructive interference or bright fringe.
(2). Destructive interference:- According to the Young’s theory, when the path difference
between the light waves is (2n±1)λ/2 then produce the destructive interference or dark fringe.
1.(a).NEWTON’S RING
INTRODUCTION :-
When a Plano convex lens of large radius of curvature is placed with its convex
surface in contact with glass plate, then a thin air film is formed between the large surface of
the lens and the upper surface of the plate. At the point of contact the air film is zero.
When the monochromatic light is allowed to fall normally on this film then a system of
alternate bright and dark rings concentric rings are observed with centre at the point of
contact of lens and plate. Each fringe is formed on the locus of points of equal thickness,
which is a circle with point of contact as centre. Such circular rings were first produced by
Newton, so they are known as Newton’s Rings.
EXPERIMENTAL ARRANGEMENT :-
Prahalad ‘Holiwala’ () 3
, In this experiment, S is a monochromatic source (Sodium light source) of light at the
focus of lens L, so a horizontal parallel beam of light falls on the glass plate P, which is
inclined at 450 to the incident beam. The inclined glass plate P reflects a part of incident light
towards the air film enclosed by the plano-convex lens and glass plate. The reflected light
from the upper surface and lower surface of the air thin film is interfere to each other and
produce the interference pattern in the form of circular dark and bright fringes. These circular
fringes are observed by the microscope.
Working:-
When a light ray AB falls normally on a plano-convex lens, light rays BR1 and CR2
reflected back from the top and bottom surface of the air thin film.
Prahalad ‘Holiwala’ () 4
