• Call Now

1800-102-2727 •

# HC Verma for Class 11 Physics Chapter 18:Geometrical Optics

Geometrical optics deals with and describes the behaviour of light rays. Chapter 18 Geometrical Optics deals with the concepts involved in different types of mirrors. It focuses on three laws involved in geometric optics. These include:

• The law of rectilinear propagation: This law states that light always travels in a straight line when travelling through a region with a constant refractive index.
• The law of reflection: The second law of Geometrical optics states that the ray of light reflected off the interface dividing two optical mediums will be in the same plane of incidence. Moreover, the angle of incidence and angle of reflection will be the same.
• The law of refraction: This law stipulates that a ray of light refracted from the interface dividing the two media will remain in the same place as the incident ray. Also, the sine of the angle of incidence will be proportional to the sine of the angle of refraction.

The chapter further focuses on the different phenomena involved. The incident ray is the original ray of light that strikes a mirror, and upon getting reflected, it is known as the reflected ray. The angles of incidence and reflection are always measured with respect to the normal. Simply put, the normal is a perpendicular line to the surface. Moreover, it is the point where the incident ray reflects off the surface. The plane containing the incident ray reflected ray, and normal is called the plane of incidence. It is perpendicular to the reflecting surface.

The incident angle is formed between the incident ray and the normal. Similarly, the reflected angle is formed between the outgoing ray and the normal. With reference to the law of reflection, the incident angle equals the reflected angle, and it applies to all reflecting surfaces. Thus, regular reflection is nothing but the reflection observed from a smooth surface, such as a mirror.