Lenses – Old is Gold



  1. At what distance from a convex lens should an object be placed on the axis so as to form a real image of the same size? Illustrate your answer with a ray diagram.
  2. Under what conditions does a concave lens form a real image?
  3. Does the focal length of a lens change if it is immersed in water? Will it increase or decrease?
  4. Draw the ray diagram showing the formation of a virtual image by a convex lens.
  5. Can a concave lens form a real image? Give the condition.
  6. Does the focal length of a lens change when immersed in water? Will it increase or decrease?
  7. A lens made of glass is immersed into water. Will its power increase or decrease?
  8. Draw the ray diagram showing the formation of real image by a concave lens.
  9. If a converging lens and a diverging lens having the same focal length be in contact, how will the combination of lenses behave?