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 focus and optical centre on the same side as that of the object.

What is the minimum number of rays required for locating the image formed by a concave mirror for an object. Draw a ray diagram to show the formation of a virtual image by a concave mirror.

The refractive indices of glass and water with respect to air are 3/2 and 4/3 respectively. If speed of light in glass is 2×108 m/s, find the speed of light in water.

What kind of lens can form:

1. An inverted magnified image?
2. An erect magnified image?
3. An inverted diminished image?
4. An erect diminished image?

Your eye contains a convex lens. Why is it unwise to look at the sun?

Define:

1. Principal focus of a concave mirror.
2. Focal length of a concave mirror.

Where would the image be formed by a convex mirror if the object is placed:

1. Between infinity and pole of the mirror?
2. At infinity?

Draw labelled ray-diagrams to show the formation of image in both the cases.

If the magnification of a body of size 1m is 2, what is the size of the image?

A star appears slightly higher (above) than its actual position in the sky illustrate it with the help of a labelled diagram.