When an object is placed at a distance of 36cm from a convex lens, an image of the same size as the object is formed. What will be the nature of image formed when the object is placed at a distance of:

1. 10cm from the lens?
2. 20cm from 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 the focus and device, image formed is enlarged and on the same side as that of the object.

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

What is meant by ‘refraction of light’? Draw a labelled ray diagram to show the refraction of light.

With the help of a diagram, show how when light falls obliquely on the side of a rectangular glass slab the emergent ray is parallel to the incident ray.

List four characteristics of the images formed by plane mirrors.

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

Which type of mirror is used in a solar furnace? Support your answer with reason.

If the image formed by a spherical mirror for all positions of the object placed in front of it is always erect and diminished, what type of mirror is it? Draw a labelled ray diagram to support your answer.

If a ray of light enters from alcohol to air. The refractive index of alcohol is 1.36. Calculate the speed of light in alcohol with respect to air.