We have already studied the converging and diverging nature of spherical lenses.
Now let us look at the activity that explains the image formed by the convex lens.
- Take a convex lens.
- Draw five parallel straight lines on a long table with chalk so that the distance between the successive lines equals the focal length of the lens.
- Place the lens on a lens stand.
- Place it so that the optical centre of the lens is just over the line on the central line.
- The two lines on either side of the lens correspond to \(F\) and \(2F\) of the lens, respectively.
- Mark them with the appropriate letters, such as \(2\), , , and \(2\). Place a burning candle far to the left of \(2\).
- On a screen on the other side of the lens, get a clear, sharp image. Make a note of the image's nature, location, and relative size.
- Place the object behind \(2\), between and \(2\), at , and between and \(O\) to repeat the activity.
- Make a list of your observations and tabulate them.
Image formation by convex lenses:
Object at infinity
Between and \(2\)
Between and \(O\)
The nature, position and relative size of the image formed by a convex lens for various object positions are summarised in the table below.