lOMoAR cPSD| 33692931
lOMoAR cPSD| 33692931
LIGHT
Sub: Physics
Topic: Interference of Light
For all school, college, and university
students
Summary: Here I have discussed the
interference of light waves and the
types of interference. I have also
provide some valuable formula for
problem solve and discussed some
problem by using the formula
, lOMoAR cPSD| 33692931
Interference of Light
1.1. Introduction:
What is light?
Light is form of energy. It is transferred from the source of light to the eye, either by the motion of
material particles or by means of wave disturbance travelling through the medium.In the late 1600s,
important questions were raised, asking if light is made up of particles, or is it waves?
Sir Isaac Newton, held the theory that light was made up of tiny particles. In 1678, Dutch physicist,
Christiaan Huygens, believed that light was made up of waves vibrating up and down perpendicular
to the direction of the light travels, and therefore formulated a way of visualizing wave propagation.
This became known as 'Huygens' Principle'. Huygens theory was the successful theory of light
wave motion in three dimensions. Newton's theory came first, but the theory of Huygens, better
described early experiments.
1.2. Wavefront:
We drop a small stone on a calm pool of water, waves spread out from the point of impact. Each
point on the surface starts oscillate with same amplitude and same phase. According to wave
theory, a point source of light when placed in an isotropic medium emits light waves in all
directions. These waves spread out uniformly in the form of ever increasing concentric spheres
with a velocity of 3 x 108 m/sec. The disturbance will reach simultaneously to all particles lying
on the surface of a sphere with the point source as the center. Such a locus of points, which oscillate
in phase is called a wavefront.
Definition:
Wave front is defined as a continuous locus of all the neighbouring points vibrating in the same
phase i.e. having same phase at a given instant of time.
Properties of wave front:
The shape of wavefront depends on the shape of the source of disturbance.
A wavefront is always normal to the light rays.
1.
2. A wavefront does not propagate in the backward direction.
The line along which energy is propagated is called a ray. It is perpendicular to wavefront at any
point.
, lOMoAR cPSD| 33692931
Source
Figure 1.1 Wavefront propagating from a point source
1.3. Type of wavefront:
It is generally of three types:
1) Spherical wavefront, 2) Plane Wavefront and 3) Cylindrical Wavefront as shown in fig. 1.2.
1) Spherical wavefront:
A wavefront in the form of spherical surfaces is
called spherical wavefront.It is obtained from a
point source of light up to a finite distance.
2) Plane Wavefront:
A wavefront in the form of plane surface is called
plane wavefront. It is obtained by keeping
pointsource at a focus of a convex lens or at a
large distance from the point source. Figure 1.2
3) Cylindrical Wavefront:
The wavefront in the form of cylindrical surface is a cylindrical wavefront. It is obtained from an
extended light source.
1.4. Huygens Principle:
According to Huygens, a source of light sends out waves in all
directions, through a hypothetical medium called ether. It gives
geometrical method to obtain the new position of the wavefront
after some time.
According to Huygens Principle
(a) Each point on a wave front behaves as a secondary source
of light and sending secondary wavelets in all possible
directions with the velocity of light so long as they move Figure 1.3
in the same medium.
lOMoAR cPSD| 33692931
LIGHT
Sub: Physics
Topic: Interference of Light
For all school, college, and university
students
Summary: Here I have discussed the
interference of light waves and the
types of interference. I have also
provide some valuable formula for
problem solve and discussed some
problem by using the formula
, lOMoAR cPSD| 33692931
Interference of Light
1.1. Introduction:
What is light?
Light is form of energy. It is transferred from the source of light to the eye, either by the motion of
material particles or by means of wave disturbance travelling through the medium.In the late 1600s,
important questions were raised, asking if light is made up of particles, or is it waves?
Sir Isaac Newton, held the theory that light was made up of tiny particles. In 1678, Dutch physicist,
Christiaan Huygens, believed that light was made up of waves vibrating up and down perpendicular
to the direction of the light travels, and therefore formulated a way of visualizing wave propagation.
This became known as 'Huygens' Principle'. Huygens theory was the successful theory of light
wave motion in three dimensions. Newton's theory came first, but the theory of Huygens, better
described early experiments.
1.2. Wavefront:
We drop a small stone on a calm pool of water, waves spread out from the point of impact. Each
point on the surface starts oscillate with same amplitude and same phase. According to wave
theory, a point source of light when placed in an isotropic medium emits light waves in all
directions. These waves spread out uniformly in the form of ever increasing concentric spheres
with a velocity of 3 x 108 m/sec. The disturbance will reach simultaneously to all particles lying
on the surface of a sphere with the point source as the center. Such a locus of points, which oscillate
in phase is called a wavefront.
Definition:
Wave front is defined as a continuous locus of all the neighbouring points vibrating in the same
phase i.e. having same phase at a given instant of time.
Properties of wave front:
The shape of wavefront depends on the shape of the source of disturbance.
A wavefront is always normal to the light rays.
1.
2. A wavefront does not propagate in the backward direction.
The line along which energy is propagated is called a ray. It is perpendicular to wavefront at any
point.
, lOMoAR cPSD| 33692931
Source
Figure 1.1 Wavefront propagating from a point source
1.3. Type of wavefront:
It is generally of three types:
1) Spherical wavefront, 2) Plane Wavefront and 3) Cylindrical Wavefront as shown in fig. 1.2.
1) Spherical wavefront:
A wavefront in the form of spherical surfaces is
called spherical wavefront.It is obtained from a
point source of light up to a finite distance.
2) Plane Wavefront:
A wavefront in the form of plane surface is called
plane wavefront. It is obtained by keeping
pointsource at a focus of a convex lens or at a
large distance from the point source. Figure 1.2
3) Cylindrical Wavefront:
The wavefront in the form of cylindrical surface is a cylindrical wavefront. It is obtained from an
extended light source.
1.4. Huygens Principle:
According to Huygens, a source of light sends out waves in all
directions, through a hypothetical medium called ether. It gives
geometrical method to obtain the new position of the wavefront
after some time.
According to Huygens Principle
(a) Each point on a wave front behaves as a secondary source
of light and sending secondary wavelets in all possible
directions with the velocity of light so long as they move Figure 1.3
in the same medium.
