how do you verify expwrimentally that the focal length of a convex lens is increased when it is kept in water.
Answers
Explanation:
Aim: To verify that the focal length of a convex lens is increased when it is kept in water.
Materials required: Convex lens, tumbler, water, circular lens holder, stone
Procedure:
• Take a convex lens of focal length & a tumbler whose height is known and is four times the focal length of lens.
• Put the stone into the tumbler. Pour some water upto the level where the height of level should be greater than the focal length of lens.
• Now dip the lens horizontally using the lens holder.
• Set the distance between the lens & the stone such that the distance is equal or less than the focal length of the lens.
• Look at the stone through the lens. The stone is visible at this stage.
• Now slowly increase the distance between the lens & stone.
• As soon as the distance gets greater than the focal length, the stone will be not visible anymore.
Conclusion: If the lens is dipped to a certain height which is greater than the focal length of lens in air, the image is clearly visible. Thus the focal length of lens is increased in water.