You have been provided with a rectangular glass prism, optical pins, and other necessary apparatus. Using the above diagram as a guide, carry out the following instructions:

1. Fix the drawing paper provided to the drawing board
2. Place the glass prism on the drawing paper and trace the outline, ABCD of the prism
3. Remove the prism, mark a point O on AB such that AO is about one-quarter of AB
4. Draw a normal through point O. Also draw an incident ray to make an angle i = 25 with the normal at O. Fix two pins at P\(_{1}\) and P\(_{2}\) On the incident ray.
5. Replace the prism. Fix two other pins at P\(_{3}\) and P\(_{4}\) such that the pins appear to be in a straight line with the images of the pins at P\(_{1}\) and P\(_{2}\) when viewed through the block along DC
6. remove the prism. Join points Pa and P4 and produce it to meet DC at 1. Also, draw a line to join Ol (
7. With O as center and using any Concinient radius, draw a circle to Cut the incident ray and the refracted ray at E and H respectively. Maintain this radius throughout the experiment
8. Draw the perpendiculars EF and GH. Measure and record d= EF and I= GH.
9. Repeat the procedure for four other values of i = 35°, 45, 55°, and 65° respectively. In each case measure and record d and I
10. Plot a graph of d on the vertical axis against I on the horizontal axis
11. Determine the slope of the graph
12. State two precautions taken to ensure accurate results. [Attach your traces to your answer booklet)

(b)i. State Snell's law.

ii. Calculate the critical angle for a water-air interface. [refractive index of water = \(\frac{4}{3}\)]