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Refraction of Light
® The bending of light at the interface between
two different mediums is called Refraction of
light.
® If the velocity of light In medium is more, then
the medium is called optical rarer.
® If the velocity of light in medium [s less is called
optical denser.
Refraction of light:
® It represents the amount of bending of light
when it passes from one medium to another
These are of two types:
® Relative Refractive index
® Absolute refractive Index
Refractive index of one medium to another is
called Relative refractive index.
® Refractive index of medium 1 with respect to
medium 2
N2:= Speed of light in medium 1/Speed of light
in medium 2 = vi/w2
® Refractive indexof medium 1 with respect to air
or vaccum.
Nw= Speed of light in airf Speed of light in
medium 1 =c/v
Laws of Refraction:
® The incident ray, refracted ray and the normal
at the point ofincidence all lie in same plane.
® The ratio of the sin of the angle of incidence to
the sin of the angle of refraction is constant.
Sin i/Sin r= Constant (u).
Refraction through plass slab and principle of
reversibility of light:
* Consider a rectangular slab, a slow in figure. A
ray incident on the face at an angle of incidence
(i). On the entering the glass slab, it bends
towards normal and travels along at an angle of
* Aray of light which ts parallel t the principal axis
will pass through the principal focus after
refraction from the lens.
* Aray of light passing through principal focus
will emerge parallel to principal axis.
® Aray of light passing through optical center will
emerge out without any deviation.
Image formation by convex lens:
* When object is at infinity:
* When object is at 2f,
* When object is placed betweenF, and 0:
Image formation by concave lems:
® When object is placed at infinity:
Image formation by convex lens
