Geometrical Optics and Postulates

Geometrical Optics

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• Geometrical optics, also known as ray optics, is a branch of optics that studies light behavior in terms of rays and their characteristics, such as reflection, refraction, and dispersion.
• It describes the propagation of light as straight-line rays in simplified scenarios, ignoring wave properties of light, such as interference and diffraction.
•  Geometrical optics is commonly used to analyze the behavior of light in situations involving lenses, mirrors, and other optical devices. It provides a simplified framework for understanding and predicting the behavior of light in optical systems.
  

The postulates of geometrical optics

1. Light travels in straight lines: 

Light is assumed to propagate in the form of rays that travel in straight lines called light rays. These rays represent the direction of the wavefront perpendicular to the rays.

2. Law of reflection: 

The incident ray, the normal line at the point of incidence, and the reflected ray all lie on the same plane. The angle of incidence (the angle between the incident ray and the normal line) is equal to the angle of reflection (the angle between the reflected ray and the normal line).

3. Law of rectilinear propagation:

 If light travels from one medium to another, it travels along a straight line path called a normal ray. This occurs as long as the media have uniform properties and no obstructions exist.

4. Law of refraction: 

When light passes from one medium to another with a different refractive index, the light ray changes direction at the boundary or interface between the media. This change in direction is characterized by the angle of refraction, which is determined by Snell's law.

5. Principle of reversibility: 

The path of light can be reversed; thus, the path taken by a light ray from a source to an observer is the same as the path taken by a light ray from the observer back to the source.

6. Principle of superposition: 

When two or more rays of light meet at a point, the resultant intensity or brightness is the algebraic sum of the individual intensities of the rays. This principle is also applicable to the interference and diffraction of light.

These postulates form the foundation of geometrical optics, allowing for the analysis of light propagation, reflection, refraction, and other optical phenomena.