Assertion A ray of light passing through the centre of curvature of a concave mirror is reflected back along the same path.

Reason The incident ray, the reflected ray and the normal at the point of incidence lie on the same plane.

1. Both Assertion and Reason are true.
2. Both Assertion and Reason are false.
3. Assertion is false but Reason is true.
4. Assertion is true but Reason is false.

If temperature of medium increases, then critical angle

1. decreases
2. increases
3. zero
4. first increases then decreases

If current through a resistance is doubled and its resistance made one-fourth, then the value of power dissipation will

1. remain same
2. double
3. become 4 times
4. become 1⁄4 time

A bar magnet is used to pick up an iron nail. At which parts of the nail it is easiest for the magnet to pick it up?

1. At end X
2. At mid-point Y
3. At end Z
4. Same at all points