Theory:

We studied the converging and diverging nature of spherical lenses. Now let us look at activity that explains the image formed by the concave and convex mirrors.
  • 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 \(2\)F1, F1, F2, and 2F2. Place a burning candle far to the left of \(2\)F1.
  • 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 \(2\)F1, between F1F1 and \(2\)F1 at F1, and between F1and O to repeat the activity.
  • Make a list of your observations and tabulate them.
Image formation by convex lenses:
 
When an object is placed at infinity, a real image is formed at the principal focus. The size of the image is much smaller than that of the object.
 
Screenshot 2021-10-07 162157.png
Object at infinity
 
When an object is placed behind the centre of curvature (beyond C), a real and inverted image is formed between the centre of curvature and the principal focus. The size of the image is smaller than that of the object.
 
Screenshot 2021-10-07 162242.png
Object is placed behind the curvature
 
When an object is placed at the centre of curvature, a real and inverted image is formed at the other centre of curvature. The size of the image is the same as that of the object.
 
Screenshot 2021-10-07 162303.png
Object is placed at the center of curvature
 
When an object is placed in between the centre of curvature and principal focus, a real and inverted image is formed behind the centre of curvature. The size of the image is bigger than that of the object.
 
Screenshot 2021-10-07 162325.png
Object is placed in between the centre of curvature and principal focus
 
When an object is placed at the focus, a real image is formed at infinity. The size of the image is much larger than that of the object.
 
Screenshot 2021-10-07 162339.png
Object is placed at the focus
 
When an object is placed in between principal focus and optical centre, a virtual image is formed. The size of the image is larger than that of the object.
 
Screenshot 2021-10-07 162405.png
Object is placed in between principal focus and optical centre