You are provided with an illuminated object, converging lens, screen, metre rule, and other necessary materials.
- Measure and record the size a\(_{o}\) of the illuminated object.
- Place the object O and the screen S on Opposite sides of the converging lens L.
- Set the distance between the object and the lens U = 30cm.
- Adjust the screen until a sharp image of the illuminated object is obtained on the screen.
- Measure and record the size a of the image.
- Evaluate m = \(\frac{a}{a_{0}}\), and m\(^{-1}\)
- Repeat the procedure for four other values of U=35cm, 40cm, 45cm and 50cm respectively.
- Tabulate your readings.
- Plot a graph with m\(^{-1}\) on the vertical axis and U on the horizontal axis.
- Determine the slope, s, of the graph and intercept, C, on the vertical axis.
- Determine the value of U for which m\(^{-1}\)=0.
- State two precautions taken to obtain accurate results.
(b)i. Using your graph, determine the value of m for which U= 37cm.
ii. Sketch a diagram to illustrate how a converging lens may be used to produce a real diminished image of an object.
Explanation
a = 1.5cm
| u/cm | \(\frac{a}{cm}\) | M=\(\frac{a}{d}\) | m\(^{-1}\) |
| 30.0 | 2.2 | 1.467 | 0.682 |
| 35.0 | 1.5 | 1.000 | 1.000 |
| 40.0 | 1.2 | 0.800 | 1.250 |
| 45.0 | 0.9 | 0.600 | 1.667 |
| 50.0 | 0.7 | 0.467 | 2.141 |
Slope (s) = \(\frac{\bigtriangleup {m}^{-1}}{\bigtriangleup {y}}\) = \(\frac{2.4 - 0.4}{54 - 24} = \frac{2}{30}\) = 0.06
X\(_{1}\) = when m\(^{-1}\) = 0
u = 23cm
Precautions; i
- avoided error due to parallel when taking readings on the metre rule.
- made sure that, I took the height of the image when it is sharp.
- ensured that the intensity of the source of light was maintained.
- took repeated readings to avoid random errors.
(b)i. When U iss 37cm
37 = 1.01m\(^{-1}\)
37 x \(\frac{1.01}{m}\)
m = \(\frac{1.01}{37}\)
m = 0.03
ii. Object beyond 2F\(^{1}\)
