Answer is 6.
Water of mass 5 kg in a closed vessel is at a temperature of 20 , \(^\circ\text{C}\). If the temperature of the water when heated for a time of 10 minutes becomes \(30 \ , ^\circ\text{C}\), then the increase in the internal energy of the water is:
Two identical concave mirrors each of focal length $ f $ are facing each other as shown. A glass slab of thickness $ t $ and refractive index $ n_0 $ is placed equidistant from both mirrors on the principal axis. A monochromatic point source $ S $ is placed at the center of the slab. For the image to be formed on $ S $ itself, which of the following distances between the two mirrors is/are correct: