Expt: Determine Focal Length of a Convex Lens


Aim: To determine the focal length of a convex lens.



  1. Fix the convex lens in the holder and place it securely on the optical bench.
  2. Switch on the light box.
  3. Move the screen (and the lens, if required) until you get a sharp image of the illuminated cut-out in the light box.
  4. Record the different distances, namely the object distance and the screen distance.
  5. Calculate the focal length of the convex lens from the given equation.
  6. Repeat the experiment with a lens of different focal length.