List of top Physics Questions on spherical lenses asked in JKCET

A convex lens of focal length $ f = 20 \, \text{cm} $ is combined with a diverging lens of power 65 D. The power and the focal length of the combination is
According to the thin lens formula, which one of the following is true regarding the focal length of the lens?
A convex lens is dipped in a liquid whose refractive index is equal to the refractive index of the lens. Then what is its focal length?
The power of a convex lens is $2 $ dioptre. Its power is to be reduced to $1.5$ dioptre, by putting another lens in combination with it. Which of the following lenses will serve the purpose?