## Questions

Question 1

You are provided with the following apparatus:-

- A rectangular glass slab.
- A soft board.
- White sheets of paper.
- 4 optical pins.
- Four tamp pin

NB: You should have mathematical tables / calculator, geometrical set and a transparent ruler.

Proceed as follows:

- Fix a white sheet of paper on the soft board using tamp pins.
- Place the glass slab on the white piece of paper. Trace the outline of the glass slap on the paper.
- Stick two pins P1 and P2 so that the line joining them falls on the edge of the glass obliquely, forming an angle of 150 with normal NA.
- Stick two other pins P3 and P4 so that they appear to be in line with the images of object pins P1 and P2 in the slab as shown on the diagram below.
- Now remove the slab. Draw the lines joining P1 and P2 and P3 and P4. Extend the two lines to meet the outline of the block at the points A and B respectively. The lines P1 and P2, AB and P3 and P4 show the path the ray follows as it passes from one medium to another: air to glass and back to air again. Mark the direction with arrows.
- Measure the angle of refraction (r) between AB and the normal. Record it in the table below. Repeat the procedure for angles of incidence of 300, 450, 600 and 750 and record the values in the table below. (8mks)
Angle of incidence (i°) 15° 30° 45° 60° 75° Angle of refraction (r°) Sin i° Sin r° - Draw a graph of sin i° (Y-axis) against sin r° (X-axis) in the grid provided below. (5mks)
- Determine the gradient of the graph. (3mks)
- Compare the value of refractive index, n, if n = sin i / sin r using a point on the graph. (2mks)

NB: Remember to hand in the pieces of white sheet of paper you used. (1mk)

Question 2

You are provided with following apparatus

- A pendulum bob
- A cotton thread 1m long
- A retort stand and clamp
- A metre rule
- A stopwatch
- Some cellotape

Proceed as follows

- Clamp the pendulum as shown starting with L=80cm
- Give the bob a small displacement and record the time t for 20 complete oscillations. Record also periodic time T for one complete oscillation.
- Repeat the procedure above for values of L as shown in the table. Record and complete the table.(8marks)
Length L (cm) L (m) Time for 20 oscillations Period T (T ^{2})

(s^{2})80 70 60 50 40 30 20 - Plot the graph of T against L(m)(5marks)
- Determine the slope of the graph(3marks)
- The equation for the graph is given by T2 = 4π²L/g where g is a constant. From the graph find the value of g.(3marks)
- What is the significance of g.(1mark)

## Confidential

- Question 1
- A rectangular glass slab.
- A soft board.
- White sheets of paper.
- 4 optical pins.
- Four tamp pin
- mathematical tables / calculator,
- geometrical set and a transparent ruler.

- Question 2
- A pendulum bob
- A cotton thread 1m long
- A retort stand and clamp
- A metre rule
- A stopwatch
- Some masking tape

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