Finding The Focal Length Of A Lens Essay

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Finding the Focal Length of a Given Convex Lens Aim: -

To find the focal length of a given convex lens.

Apparatus: -

Convex lens Metre rule

Screen Candle

Matches Wooden blocks

Theory:-

In this experiment the focal length of a lens is found out. The focal lens of a lens is the distance from the principal focus to the optical centre. It is the point where the image comes into focus when seen though the lens. The focal length of a lens depends on the curvature of each surface. So the more highly …show more content…

The independent variable is the distance d, the distance between the screen and the illuminated object.

The controlled variable is the intensity of the illuminated object and the focal length of the lens

Procedure

1. Place the illuminated object at a distance of 50 cm from the screen and set up the apparatus as shown in the figure above.

2. Now place the lens somewhere close to the screen and see in which position of the lens does the illuminated object comes into focus on the screen.

3. Mark this position as L1 and record its distance from the illuminated object.

4. Now place the lens somewhere close to the illuminated object where the object comes into focus on the screen.

5. Mark this position as L2 and record its distance from the illuminated object.

6. Repeat the experiment for values ranging from 50 cm to 100 cm.

7. Tabulate six sets of the values of d, L1, L2, l and l 2/d.

8. Plot a graph of l 2/d against d.

9. From the graph, find the y- intercept of the graph and

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