A transformer supplies 12V when connected to a 240V mains. If the transformer takes 0.120A from the mains when used to light a 12V, 24W lamp, what is its efficiency?

Which of the following is/are TRUE of nuclear fission?

I. A heavy nucleus is split into two nuclei of comparable masses.
II. Two light nuclei are joined together to form a heavier nucleus.
III. The total mass of the products is less than that of the reactants.

A converging lens of focal length 5cm forms a virtual image which is 20cm from the lens. How far from the lens is the object?