Draw ray diagrams showing the image formation by a convex lens when an object is placed:At twice the focal length of the lens.

Explain with the help of a diagram, why the concave lens is also called a diverging lens.

A large concave mirror has a radius of curvature of 1.5m. A person stands 10m in front of the mirror. Where is the person’s image?

If a ray of light is incident on a plane mirror such that it makes an angle of 30with the mirror, then will be the angle of reflection?

What is observed when 2mL of dilute hydrochloric acid is added to 1g of sodium carbonate taken in a clean and dry test tube? Write chemical equation for the reaction involved.

The boy walks towards the mirror at a speed of 1m/ s. At what speed does his image approach him?

A 5cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 18cm at a distance of 12cm from it. Use lens formula to determine the position, size and nature to the image formed.

An object is placed at a distance of 15 cm. from a convex lens of focal length 20 cm. List four characteristics (nature, position, etc.) of the image formed by the lens.

Identify the device used as a spherical mirror or lens in following cases, when the image formed is virtual and erect in each case.Object is placed between infinity and device, image formed is diminished and between pole and focus, behind it.

The optician’s prescription for a spectacle lens is marked +0.5D. What is the:

1. Nature of spectacle lens?
2. Focal length of spectacle lens?