An object is placed at the centre of curvature of a concave mirror of focal length 16 cm. If the object is shifted by 8 cm towards the focus, then the nature of the image would be

A pencil is placed upright at a distance 10 cm from a convex lens of focal length 15 cm. The nature of the image of the pencil will be

Which one of the following is a conventional energy source?

A container is first filled with water and then the entire water is replaced by mercury. Mercury has a density of 13.6 $$\times$$ 10³ kg/m³. If X is the weight of the water and Y is the weight of the mercury, then