Ans: Deviation of ray of light from its original path when it travels from one transparent homogeneous medium to another transparent homogenous medium is called the refraction of light.
There are two laws of refraction :-
(I ) incident ray, reflected ray and normal lie in the same plane.
(ii) The ratio of sine of angle of incidence and sine of angle of refraction is constant i.e. Sin i / Sin r = n. This is also called as Snell’s law.
Q. Define Refractive Index:
Ans: It is the ratio of speed of light in vacuum to the speed of light in medium is called Refractive index.
Q. Give the ratio of velocities of two light waves travelling is vacuum and having wave lengths 4000A0 and 8000A0.
Ans: In Vacuum, light of all the wave lengths travel with the same velocity i.e. 3 X 108 m/sec.
Q.. For what angle of incidence, the lateral shift produced by parallel sided glass plate is zero?
Ans: For <i = 0.
Q. What are the factors on which the lateral shift depends?
Ans: Thickness of the refracting medium, angle of incidence and its refractive index
Q. What is the value of Relative refractive index of air?
Q. If speed of light in vacuum = 3 x 108 m/sec and Refractive index of water = 4/3, What is the speed of light in water?
Ans: Refractive index of water = Speed of light in vacuum / Speed of light in water;
4/3 = (3 x 108 m/sec )/ (Speed of light in water)
Speed of light in water = (3 x 108 m/sec) x ¾ = 9/4 x 108m/sec = 2.25 x 108 m/sec.
Q. For the same angle of incidence in media P, Q and R, the angles of refraction are 350, 250, 150 respectively. In which medium will the velocity of light be minimum?
Ans: According Snell’s law n = Sin i / Sin = C / V
For given angle of incidence (i), V will be minimum, when angle of refraction <r is minimum
In given data it is for medium R.
Q. A coin in a glass beaker appears to rise as the beaker is slowly filled with water. Why?
Ans: It happens on account of refraction of light. A ray of light starting from the coin goes from water to air and bends away from normal. Therefore, bottom of the beaker on which the coin lies appears to be raised.