Trace the outline ABCD of the glass block on the sheet of paper as shown in the diagram. Remove the block and draw the normal at O. Draw an incident ray such that the angle of incidence i =30°. Fix two pins at points P and Q on the incident ray. Replace the block and fix two other pins at points U and V such that the pins appear to be in a straight line with the images of the pins at P and Q when viewed through the block. Remove the block and join the points at V and U, producing the line to meet DC at T. Join OT With O as a center and using any convenient radius, draw a circle to cut the incident and refracted rays at R and S respectively. Draw the perpendiculars RN and MS. Measure and record RN and MS. Repeat the experiment for i = 40° 50° 60° and 70° respectively. In each case, determine and record the corresponding values of RN and MS. Tabulate your readings. Plot a graph of RN on the vertical axis and MS on the horizontal axis. Determine the slope s of the graph, State two precautions taken to ensure accurate results. [Attach your traces to your answer script]

(b)i. Explain refraction.

ii. Draw a diagram showing why a metre rule, partly immersed in water and placed obliquely to the surface appears bent at the surface.

Measure and record the e.m.f of the accumulator provided. Connect the circuit as shown in the diagram. With zero resistance in the resistance box, adjust the rheostat to obtain the maximum possible reading on the ammeter. Do not adjust the rheostat again throughout the experiment. Open the key. With R= 1\(\Omega\), close the key, read and record the reading of the ammeter I. Calculate 1\(^{-1}\) Repeat the experiment for R=2,3,4 and 5\(\Omega\) respectively. In each case, read and record the value of 1\(_{A}\) and calculate the Corresponding value of l\(_{A}^{-1}\). Now connect the resistor Q in series into the circuit and without altering the setting of the rheostat, record the new ammeter readings l\(_{B}\) for R= 1,2,3, 4, and 5\(\Omega\). Calculate the corresponding value of l\(_{B}\) in each case. Tabulate all your readings. On the same graph and using the same axes and scales, plot the graphs of:
(i) I\(_{A}^{-1}\)' on the vertical axis and R on the horizontal axis;
(ii) l\(_{B}^{-1}\) on the vertical axis and R on the horizontal axis. Calculate the slopes S\(_{A}\) in (i) and S\(_{B}\) in (ii) above. Determine the difference D between the intercepts of the graphs on the vertical axis. State two precautions taken to ensure accurate results.

(b) i. Explain why a battery of eight dry Leclanche cells, each of e.m.f. 1.5v is not normally used in place of a motor-car battery of 12V to start a car.

ii.  State two sources of e.m.f. other than the chemical cell.