one half of a convex lens is covered with black paper with a lens produces a complete agimage of object verify your answer expalrimenty . explain your observations.
Answers
Answer
Yes, even one and half of a convex lens is coverd with a black paper the lens will produce a complete image .
Expariment
Take a live candle keep it in front of a convex lens mounted on optical bench. Move the candle along the axis of bench and take it full image on a screen .
Now cover the lower half of lens with black paper without changing the position of candle , lens and screen.
Observation
You will observe that full image of candle is still seen on the screen ; but the instantly of image is reduced .
Reason
The reason is that a large number of it is turned on the length and Blocked. In the case of the covered lower half of lens with black paper the rays that are emerging from candle and incident on lens are reflected from upper path only and from the full image.
Answer:
A point on the object needs only two rays to form an image. Since the entire lens is not covered, at least two rays from each point does pass through the lens and hence, image is formed. However, since the number of rays involved in the image formation reduces as the lens is covered, the image formed is of lesser intensity and less brighter.
Experiment:
Apparatus needed: convex lens, candle, two black sheets of paper.
Procedure:
Mount a lens on a table. Light a candle with a match stick and place it on one side of the lens on the table. Turn of the lights of the room so that it gets dark. Take the sheet of paper and place it on the other side of the lens as the candle. Now focus the image formed on the sheet of paper by moving the sheet only. Observe the image. Mark the positions of candle, lens and screen. Now, turn off the light. Take the lens and cover half of it with the second sheet of black paper. Mount the lens on the table in the original position and repeat the above experiment.
Observations:
Observations:A focussed image is obtained in both the experiments. However, the image formed with half the lens covered is less bright as compared to when it is uncovered.
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