Physics for IITJEE:Optics Short Notes-1

Agenda :Summary of the basics of Optics

Reflection of light
-When light travelling in one medium is incident on a second medium some part of it is sent back to the first medium according to some definite laws and is said to be reflected.
-In practice mirrors are used to reflect light.
-The angle which the incident ray and the reflected ray make with normal to the surface are termed as Angles of incidence and of reflection respectively.

Laws of reflection:-
Law 1- The incident ray, the reflected ray and the normal to the surface , all lie in the same plane.
Law 2- The angle of incidence i is equal to the angle of reflection r.

Spherical Mirrors :-
Assuming that all the reflecting surfaces are portions of a sphere, if the inside surface reflects, the mirror is concave and if the outside surface which reflects, it is convex as shown below in the figure.
-Relation between focal length f and radius of curvature R of the mirror is
f=R/2
and both f and R are taken as positive for concave mirror and negative for convex mirror.
-Mirror formula is the relation between distance of the object (u), distance of the image (v) and the focal length (f) of the mirror and is,
(1/u)+(1/v)=(1/f)
-Mirror formula holds for a spherical mirror of small aperture only.
-The ratio of size of the image formed (by spherical mirror) to the size of the object is called magnification. Mathematically,
m=I/O
=-v/u
-Spherical abberation is the inability of a spherical mirror of large aperture to bring all the rays of wide beam of light falling

on it to focus at a single point.











More information will be given in subsequent post

Please let us know if you like this post and what can be done to improve on that
Please comments

Popular Posts