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.
Explanation
Table of values/observation
| S/N | 1°(degree) | RN(cm) | MS(cm) |
| 1 | 30.00 | 1.00 | 0.70 |
| 2 | 40.00 | 1.35 | 0.90 |
| 3 | 50.00 | 1.60 | 1.05 |
| 4 | 60.00 | 1.80 | 1.20 |
| 5 | 70.00 | 2.00 | 1.30 |
Slope (s) = \(\frac{\bigtriangleup {RN(cm)}}{\bigtriangleup {MS(cm)}} = \frac{2.16-0.1}{1.4-0.18} = \frac{2.06}{1.22}\) = 1.688
Precautions:
- Ensure that the pins are vertical
- Ensure reasonable spacing of pins.
(b) Refraction is the change in the direction of a ray of light at the boundary between two media as a result of the change in the speed of light at the boundary.
