[C] negative, positive If an image formed behind the concave mirror, the object distance is positive but if an image is formed in front of the mirror, the image distance is negative.

The white solid, lead carbonate is heated and decomposes into yellow coloured lead oxide and carbon dioxide. So, “X” is lead oxide.

Try to understand – nA = sin i/sin r = sin 45°/sin 45° = 1 nB = sin i/sin r = sin 45°/sin 45° = 1/√2 x 2/1 = √2 = 1.414

The experiment should be performed on the same wall as the window. Rays from infinity will be focus at the focal point of the mirror.

Out of the metals Mg, Zn, Fe and Al, Mg will react most vigorously with dilute acid, followed by Al, Zn and Fe