S K Sharma Solutions for Chapter: Light Reflection and Refraction - Natural Phenomena, Exercise 3: UNSOLVED NUMERICALS FOR PRACTICE

A needle $10 \mathrm{cm}$ high is placed at $40 \mathrm{cm}$ from a convex lens of focal length $15 \mathrm{cm}$. Find position, nature and size of image. Also draw ray diagram.

A $5 \mathrm{cm}$ high object is placed at a distance of $10 \mathrm{cm}$ from a convex lens of focal length $15 \mathrm{cm}$. By drawing a ray diagram, find position, nature and size of image.

A needle $4 \mathrm{cm}$ high is placed in front of a lens. Image of the needle is real, inverted and $6 \mathrm{cm}$ high, when the distance between the needle and its image is $20 \mathrm{cm}$. Find the focal length of lens and also write the type of this lens.

A convex lens of the focal length $25 \mathrm{cm}$ is placed in contact with a concave lens of focal length $20 \mathrm{cm}$. Find the focal length of the combination of lenses.  

A convex lens of the focal length $25 \mathrm{cm}$ is placed in contact with a concave lens of focal length $20 \mathrm{cm}$. Find the power of the combination. What is the nature of the combination?