List four precautions which a student should observe while determining the focal length of a given convex lens by obtaining image of a distant object on a screen.

‘‘A concave mirror of focal length 15cm can form a magnified erect as well as inverted image of an object placed in front of it.’’ Justify this statement stating the position of the object with respect to the pole of the mirror in both cases for obtaining the images.

Three convex lenses are available having focal lengths of 4cm, 40cm and 4m respectively. Which one would you choose as a magnifying glass and why?

Explain with the help of a diagram, why the convex lens is also called a converging lens.

An object 1cm tall is placed 30cm in front of a convex mirror of focal length 20cm. Find the size and position of the image formed by the convex mirror.

Describe with a suitable diagram, how a convex mirror diverges a parallel beam of light rays. Mark clearly the pole, focus and centre of curvature of convex mirror in this diagram.

State two positions in which a concave mirror produces a magnified image of a given object. List two differences between the two images.

If the object is moved further away from the mirror, what changes are there in the position and size of the image?

Name the type of mirrors used in the design of solar furnaces. Explain how high temperature is achieved by this device.

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 device and its focus, image formed is enlarged and behind it.