Introduction
The branch of Physics dealing with the nature and properties of light and vision is called optics.
Nature of Light
Light is a form of energy and can be transformed into other forms of energy. You would have observed the path of 'a beam of light' inside a room.
Rectilinear Propagation of Light
In a homogenous transparent medium light travels in a straight line and this is known as rectilinear propagation of light.
Reflection of Light
When a ray of light hits a surface, it bounces off or reflects and then reaches our eyes.
Reflection of Light by a Plane Surface
The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane.
Verification of the Laws of Reflection
Repeat the experiment for different measures of angle of incidence. The laws of reflection are found to be always true for different values of angle of incidence.
Nature of the Image Formed by a Plane Reflecting Surface
An image can be real or virtual. A real image is formed when the rays of light actually intersect after reflection.
Formation of Image by a Plane Mirror - Ray Diagrams
A ray of light falling on a plane mirror at any angle gets reflected from the mirror such that the angle of incidence is equal to the angle of reflection.
Spherical Mirrors
A mirror whose polished, reflecting surface is a part of a hollow sphere of glass or plastic is called a spherical mirror.
Sign Convention for Spherical Mirrors
Distances measured in the direction of the incident ray are positive and the distances measured in the direction opposite to that of the incident rays are negative.
Formation of Images by Spherical Mirrors
When an object is placed in front of a concave mirror, light rays from the object fall on the mirror and get reflected.
Formation of Images by a Concave Mirror
The ray which is incident at the pole gets reflected according to the law of reflection and the second ray which passes through the centre of curvature of the mirror retraces its path.
Uses of Concave Mirror
The use of a concave mirror depends upon the distance of the object from the mirror.
Formation of Images by a Convex Mirror
A ray of light travelling parallel to the principal axis after reflection from a convex mirror appear to come from its focus behind the mirror.
Formation of Image in a Convex Mirror
When the Object is Placed Between Infinity and the Pole of the Mirror.
Mirror Formula (Concave Mirror)
In a spherical mirror, the distance of the object from its pole is called the object distance (u). the distance of the image from the pole of the mirror is called the image distance (v).
Magnification
Magnification produced by a spherical mirror gives the relative extent to which the image of an object is magnified with respect to the object size.
Summary
Light is a form of energy which can be reflected either by a plane mirror or spherical mirror. Depending upon the type of mirror used for reflection of light the use of reflecting surface also varies.
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Multiple Choice Questions
