Waec 2023 Physics Question 2

You are provided with a rectangular block, a drawing board, drawing sheets, four optical pins and other necessary materials. Use the diagram above as a guide to perform the experiment. (i) Measure and record the width of the block. (ii) Draw the outline ABCD of the block on a drawing sheet. Mark a point, Q on AB such that AQ=1.5 cm. Draw the normal RQT as shown in the diagram above. (iii) Draw a line UQ making an angle =10^{ extcirc} with the normal RQT. (iv) Insert pins P_{1} and P_{2} on the UQ. Look through the side DC of the block and insert two other pins, P_{3} and P_{4} which appear to be in a straight line with the images of P_{1} and P_{2}. (v) Remove the block and mark the positions of P_{3} and P_{4}. Draw a straight line joining P_{3} and P_{4} and extend it to meet DC at E. (vi) Produce a line UQ to meet DC at the point F. Draw a straight line EQ. (vii) Measure and record the angle, r, length, EF=D, and evaluate an i, an r and V=( an i- an r). (viii) Using different outlines of the block, repeat the procedure for i=20^{ extcirc}, 30^{ extcirc}, 40^{ extcirc} and 50^{ extcirc}. In each case, measure and record r, d and evaluate an I, an r and V. (ix) Tabulate the results. (x) Plot a graph with d on the vertical axis and V on the horizontal axis. (xi) Determine the slope, s, of the graph. (xii) State two precautions taken to ensure good results.

(i) State the condition for the occurrence of total internal reflection at air-glass interface. (ii) State Snell's law.