You are provided with a converging lens and holder, a screen, a ray box containing an illuminated object pin, and a meter rule. i. Place the lens in its holder such that it is facing a distant object seen through a well-lit laboratory window. Move the screen to and fro until a sharp image of the distant object is formed on it. Measure the distance, f\(_{0}\), between the screen and the lens. ii. Clamp the meter rule securely to the table. Place the illuminated object pin at the end R of the meter rule. iii. Place the lens at a position P such that X = RP = 20cm. iv. Move the screen to a position Q to receive a sharp image of the object. Measure the distance Y = PQ. v. Evaluate Z = (X+Y) vi. Repeat the procedure for five other values of x = 25cm. 3Ocm, 35cm, 40cm and 45cm. In each case, record X,Y and evaluate Z. vii. Tabulate the results. viii. Plot a graph with Z on the vertical axis and X on the horizontal axis. Draw a smooth curve through the points. ix. Determine from your graph the minimum value of Z=Z\(_{0}\) and its corresponding distance x. Evaluate W = ½ (\(\frac{Z_0}{4} + \frac{X_0}{2}\)) xi. State two precautions taken to ensure accurate results. (b) i. Draw a ray diagram to show how a Convex lens forms an image of magnification less than one. ii. Name two pairs of features in the human eye and a lens camera that performs similar functions.
Explanation
F = 13.0cm Table of value
S/N
Xcm
Ycm
Z(x+y)cm
123456
202530354045
603830262421
806360616461
Let 1cm represent5 units on the vertical axis and 1cm represent 5 units on the horizontal axis. Minimum value of Z=Z\(_{0}\) from the graph = 60cm Corresponding distance of X\(_{0}\) = 30cm Evaluate W = ½ (\(\frac{Z_0}{4} + \frac{X_0}{2}\)) = ½(\(\frac{60}{40} + \frac{30}{2}\) = ½(\(\frac{60 + 60}{4}\) = ½\(\frac{120}{4}\) = ½(30) = 15 Precautions - Coaxial arrangement of optional instruments/ray box, len and screen on a straight line. - Avoided parallax error in reading metre rule. - Lens kept uptight - Repeated reading shown on table - Surface of lens cleaned - Noted/corrected/avoided zero error on metre rule. (b)i.