Waec 2025 Physics Question 2

You are provided with a ray box, a converging lens L, a lens holder, a meter rule, a screen and other necessary apparatus in holder, and move it towards or away from the screen until (i) Place the lens L in its holder, and move it towards or away from the screen until a clear image of a distant object is formed on the screen. (ii) Determine the approximate focal length of the lens. (iii) Set up the apparatus as shown in the diagram. (iv) With \( x=70 \mathrm{~cm} \), adjust the position of the screen until a clear image of the illuminated object is formed on the screen. (v) Measure and record the distance \( y \). (vi) Evaluate \( K=\frac{x}{y} \). (vii) Repeat the procedure with \( x=60.0 \mathrm{~cm}, 50.0 \mathrm{~cm}, 45.0 \mathrm{~cm} \) and 40.0 cm and in each record \( y \) and evaluate \( K=\frac{x}{y} \). (viii) Tabulate the results. (ix) Plot a graph of \( x \) on the vertical axis and \( K \) on the horizontal axis starting both axes from the origin \( (0,0) \). (x) Determine the slope, \( s \) of the graph and the intercept, \( c \) on the vertical axis. (xi) Using the graph, determine the value of \( y \) when \( x=48.0 \mathrm{~cm} \). (xii) State two precautions taken to ensure correct results.

(i) Explain the term conjugate foci of a converging lens. (ii) A converging lens of focal length 20 cm produces a virtual image 3 times the size of the object. Calculate the image distance.