State and verify laws of refraction using a glass slab.

There are two Laws of Refraction these are –

• The incident ray, the refracted ray and the normal to the surface at the point of incidence all lie in one plane.

• For any two given pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant.

• The second law is called Snells Law after the scientist Willebrod Van Roijen Snell who first formulated it.
Thus, Sin i by Sin r (where the i is the angle of incident and r is the angle of refraction) is equal to a constant that is equal to μ where, mew is the refractive index of the second medium (R2) with respect to the first medium (R1).

Hence

There are the procedure how we can verify the laws of refraction-

• Place a rectangular glass slab on a white sheet of paper fixed to a drawing board.

• Trace the boundary A1B1C1D1 of the glass slab.

• Remove the glass slab.

• Draw IO to represent the incident ray.

• Draw the normal MN at the point of incidence O.

• Fix two pins P1 and Q1 on the incident ray IO.

• Place the glass slab within its boundary A1B1C1D1.

• Look in from the other side of the glass slab, fix two pins R1 and S1 such that the feet of all the pins are in one straight line.

• Remove the glass slab and the pins.

• Mark the pin points P1, Q1, R1 and S1.

• Join R1 S1 to represent the emergent ray O2 E.

• Join O1O2 . O1O2 dash is the refracted ray.

The incident ray, the refracted ray and the normal are all lying in the same plane. This proves the first law of refraction.

Measure and record the angle of incidence(i) and angle of refraction(r).
Repeat the experiment by varying the angle of incidence and Measure the corresponding angle of refraction.
Now find the ratio of the sine of the angle of incidence(i) to the sine of the angle of refraction(r).

The ratio of the sine of the angle of incidence to the sine of the angle of refraction is found to be the same in all the three cases.

This verifies the second law of refraction or Snells law that is sin i by sin r is equal to μ , a constant for a given pair of media.