The laws which govern the refraction of light when it passes from one transparent medium to another are called laws of refraction or Snell’s laws.
The incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.
For a given pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant.
sin i / sin r = constant
This constant is called the refractive index of the second medium with respect to the first medium.
The refractive index of a medium is defined as the ratio of the speed of light in vacuum to the speed of light in that medium.
μ = c / v
where,
c = speed of light in vacuum
v = speed of light in the medium
μ = sin i / sin r
Q1. Laws of refraction are also known as: A) Newton’s laws B) Laws of reflection C) Snell’s laws D) Kepler’s laws Answer: C Q2. According to Snell’s law: A) sin i = sin r B) sin i / sin r = constant C) i = r D) i + r = 90° Answer: B Q3. Refractive index of a medium is given by: A) v / c B) c / v C) c × v D) c − v Answer: B Q4. When light travels from air to glass, it bends: A) Away from normal B) Along the normal C) Towards the normal D) Does not bend Answer: C Q5. If angle of incidence increases, angle of refraction: A) Decreases B) Remains constant C) Increases D) Becomes zero Answer: C Q6. Which quantity remains constant for a given pair of media? A) sin i B) sin r C) sin i / sin r D) i − r Answer: C Q7. Refractive index depends on: A) Shape of medium B) Colour of medium C) Nature of medium D) Size of medium Answer: C Q8. The refractive index of vacuum is: A) 0 B) 1 C) 1.33 D) 1.5 Answer: B
Incident ray, refracted ray and normal lie in same plane.
sin i / sin r = constant
μ = c / v
Also,
μ = sin i / sin r
Numericals and MCQs are frequently asked on Snell’s law, refractive index and direction of bending.
