Definition
What is Light
Light is a type of energy. It is a form of electromagnetic radiation of a wavelength which can be detected by the human eye.Animals can also see light.
Whenever there is dark we switch ON the light so that we can see the things. As explained in figure the dark room is shown where some rays of light are coming from window and lighting the place.
Whenever there is dark we switch ON the light so that we can see the things. As explained in figure the dark room is shown where some rays of light are coming from window and lighting the place.
Law
Newton’s corpuscular theory
Newtons corpuscular theory of light is based on the following points.
1. Light consists of very tiny particles known as corpuscular.
2. These corpuscles on emission from the source of light travel in straight line with high velocity.
3. When these particles enter the eyes, they produce image of the object or sensation of vision.
4. Corpuscles of different colours have different sizes.
1. Light consists of very tiny particles known as corpuscular.
2. These corpuscles on emission from the source of light travel in straight line with high velocity.
3. When these particles enter the eyes, they produce image of the object or sensation of vision.
4. Corpuscles of different colours have different sizes.
Definition
Introduction to Newton's Corpuscular Theory of Light
The "corpuscular theory" was proposed by Newton in 1704. In this theory, he successfully explained the nature of light.
According to Newtons corpuscular theory :
According to Newtons corpuscular theory :
- Light is made up of tiny particles called corpuscles having negligible mass.
- These particles (corpuscles) are perfectly elastic.
- The corpuscles are emitted from the luminous sources such as Sun, candle, electric lamp etc.
- The tiny particles (corpuscles) always travel in a straight line in all directions.
- Each particle (corpuscle) carries kinetic energy with it while moving.The corpuscles travel at high velocity.
- The corpuscles (light) would travel faster in the denser medium than in rarer medium. But later this is proved wrong. We know that light travels faster in the rarer medium than in denser medium.
- When the particles (corpuscles) fall on the retina of the eye, they produce an image of the object or sensation of vision.
- The corpuscles can be of different sizes. The different colors of light are due to the different sizes of the corpuscles.
Definition
Failures of Newton’s corpuscular theory
Newtons Corpuscular Theory was failed due to the following assumptions :
- Newton assumed that light travels faster in the denser medium than in the rarer medium which has been proved wrong.
- The assumption that the different colors of light are due to the differences in the sizes of corpuscles has no justification.
- Newton assumed that reflection of light is due to the repulsion between the corpuscles and reflecting surface while refraction of light is due to the attraction between the corpuscles and refracting surface. Thus, a medium could either attract or repel the corpuscles of light. But later this statement was proved wrong.
- Corpuscular theory cannot explain the phenomena of diffraction, interference, and polarization of light.
Definition
Corpuscular theory about refraction of light
According to Newton, when corpuscles (light particles) approach the refracting surface, they are attracted near the surface. When they enter the denser medium from a rarer medium, their speed increases and hence change their direction.
Definition
Corpuscular theory about reflection of light
According to Corpuscular theory, light reflects in exactly the same way as a perfectly elastic ball reflects from a rigid plane.
When the corpuscles (particles) hit the reflecting surface, they are reflected from it in such a way that the angle of incidence is equal to the angle of reflection. This is due to the repulsion between the corpuscles and the reflecting surface.
When the corpuscles (particles) hit the reflecting surface, they are reflected from it in such a way that the angle of incidence is equal to the angle of reflection. This is due to the repulsion between the corpuscles and the reflecting surface.
Definition
Wavefront
A surface on which the wave disturbance is in same phase at all points is called a wavefront. For example the shape of the ripples of water when a stone is thrown in the pond.
Definition
Huygens Principle
Huygen's Principle:Various points of an arbitrary surface, when reached by a wavefront, become secondary sources of light emitting secondary wavelets.The disturbance beyond the surface results from the superposition of these secondary wavelets.
Huygens Construction: Various points of an arbitrary surface, when reached by a wavefront, become secondary sources of light emitting secondary wavelets.The geometrical envelope of these wavelets at any given later instant represents the new position of the wavefront at that instant.
Huygens Construction: Various points of an arbitrary surface, when reached by a wavefront, become secondary sources of light emitting secondary wavelets.The geometrical envelope of these wavelets at any given later instant represents the new position of the wavefront at that instant.
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