2008 WAEC Physics Practical Using the above diagram as a guide, carry out the following instructions. Fix a metre...

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Using the above diagram as a guide, carry out the following instructions.

Fix a metre rule on the bench with its graduated side facing up.
Place the illuminated object at the 0cm end and the screen at the 100cm end of the rule such that the distance d between the illuminated object and screen is 100cm.
Record the distance d. Also, evaluate and record d\(^{2}\).
Place and move the Converging lens between the illuminated object and the Screen until a sharp diminished image of the object is formed on the screen.
Read and record the position Ih of the lens.
Now move the lens towards the object until another sharp image of the object is formed on the Screen.
Read and record the new position l\(_{2}\) of the lens.
Evaluate and record L= (l\(_{1}\) - I\(_{2}\)), also evaluate L\(^{2}\) and D = d\(^{2}\) - L\(^{2}\).
Repeat the procedure for four values of d= 85, 75, 65 and 55cm. Tabulate your readings.
Plot a graph or Don the vertical axis against d on the horizontal axis.
Determine the slope, s, of the graph.
Evaluate k = \(\frac{s}{4}\).
State two precautions taken to obtain accurate results.

(b)i. Explain the statement the focal length of a converging lens is 15cm.

ii. Distinguish between a real image and a virtual image.

k = \(\frac{s}{4} = \frac{146.9}{4}\) = 36.733

Precautions:

(b)i. This means that the distance between the optical centre (or middle of lens) of the lens and its principal focus is 15cm.

Real image	Virtual image
(i) Can be received/formed on a screen (ii) Formed by the intersection of actual rays	(i) Cannot be received/formed on a screen. (ii) Formed by the intersection of imaginary rays.