Friday, October 15, 2021

Light-Reflection and Refraction | Class 10 | Activity 10.12 with Solution

Light-Reflection and Refraction | Activities in Text Book with Solution

Activity 10.12

Take a convex lens. Find its approximate focal length in a way described in Activity 10.11.

Draw five parallel straight lines, using chalk, on a long Table such that the distance between the successive lines is equal to the focal length of the lens.

Place the lens on a lens stand. Place it on the central line such that the optical centre of the lens lies just over the line.

The two lines on either side of the lens correspond to F and 2F of the lens respectively. Mark them with appropriate letters such as 2F1, F1, F2 and 2F2, respectively.

Place a burning candle, far beyond 2F1 to the left. Obtain a clear sharp image on a screen on the opposite side of the lens.

Note down the nature, position and relative size of the image.

Repeat this Activity by placing object just behind 2F1, between Fand 2F1 at F1, between F1 and O. Note down and tabulate your observations.

✅ Answer:  

Position of the object

Position of the image

Relative size of the image

Nature of
the image

At infinity

At F2

Highly diminished,

Real and inverted

Beyond 2F1

b/w F2 & 2F2


At 2F1

At 2F2

Same size

Between F1 & 2F1

Beyond 2F2


At focus F1

At infinity

Infinitely large or highly enlarged

Between F1 and optical centre O

On the same side of the lens as the object


Virtual and erect

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