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 F1 and 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 |
|
At infinity |
At F2 |
Highly
diminished, |
Real and inverted |
|
Beyond 2F1 |
b/w F2
& 2F2 |
Diminished |
“ |
|
At 2F1 |
At 2F2 |
Same size |
“ |
|
Between F1
& 2F1 |
Beyond 2F2 |
Enlarged |
“ |
|
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 |
Enlarged |
Virtual and erect |