Lakhmir Singh and Manjit Kaur Solutions for Chapter: Refraction of Light, Exercise 20: Questions Based on High Order Thinking Skills (HOTS)

A student did an experiment with a convex lens. He put an object at different distances $25 \mathrm{cm}, 30 \mathrm{cm}, 40 \mathrm{cm}, 60 \mathrm{cm}$ and $120 \mathrm{cm}$ from the lens. In each case he measured the distance of the image from the lens. His results were $100 \mathrm{cm}, 24 \mathrm{cm}, 60 \mathrm{cm}, 30 \mathrm{cm}$ and $40 \mathrm{cm}$, respectively. Unfortunately his results are written in wrong order.

Rewrite the image distances in the correct order.

A student did an experiment with a convex lens. He put an object at different distances $25 \mathrm{cm}, 30 \mathrm{cm}, 40 \mathrm{cm}, 60 \mathrm{cm}$ and $120 \mathrm{cm}$ from the lens. In each case he measured the distance of the image from the lens. His results were $100 \mathrm{cm}, 24 \mathrm{cm}, 60 \mathrm{cm}, 30 \mathrm{cm}$ and $40 \mathrm{cm}$, respectively. Unfortunately his results are written in wrong order.

What would be the image distance if the object distance was $90 \mathrm{cm}$?

A student did an experiment with a convex lens. He put an object at different distances $25 \mathrm{cm}, 30 \mathrm{cm}, 40 \mathrm{cm}, 60 \mathrm{cm}$ and $120 \mathrm{cm}$ from the lens. In each case he measured the distance of the image from the lens. His results were $100 \mathrm{cm}, 24 \mathrm{cm}, 60 \mathrm{cm}, 30 \mathrm{cm}$ and $40 \mathrm{cm}$, respectively. Unfortunately his results are written in wrong order.

Which of the object distances gives the biggest image?

A student did an experiment with a convex lens. He put an object at different distances $25 \mathrm{cm}, 30 \mathrm{cm}, 40 \mathrm{cm}, 60 \mathrm{cm}$ and $120 \mathrm{cm}$ from the lens. In each case he measured the distance of the image from the lens. His results were $100 \mathrm{cm}, 24 \mathrm{cm}, 60 \mathrm{cm}, 30 \mathrm{cm}$ and $40 \mathrm{cm}$, respectively. Unfortunately his results are written in wrong order.

What is the focal length of the lens.

A magnifying lens has a focal length of $100 \mathrm{mm}$. An object whose size is $16 \mathrm{mm}$ is placed at some distance from the lens so that an image is formed at a distance of $25 \mathrm{cm}$ in front of the lens.

What is the distance between the object and the lens?

A magnifying lens has a focal length of $100 \mathrm{mm}$. An object whose size is $16 \mathrm{mm}$ is placed at some distance from the lens so that an image is formed at a distance of $25 \mathrm{cm}$ in front of the lens.

Where should the object be placed if the image is to form at infinity?

A lens forms a real image $3 \mathrm{cm}$ high of an object $1 \mathrm{cm}$ high. If the separation of object and image is $15 \mathrm{cm}$, find the focal length of the lens.

An object $50 \mathrm{cm}$ tall is placed on the principal axis of a convex lens. Its $20 \mathrm{cm}$ tall image is formed on the screen placed at a distance of $10 \mathrm{cm}$ from the lens. Calculate the focal length of the lens.