How does quantum theory explain the working of a photocell? a. each light wave with a certain minimum energy releases an electron from an atom. b. each photon of light with energy below a certain value releases an electron from an atom. c. each light wave with energy below a certain value releases an electron from an atom. d. each photon of light with a certain minimum energy releases an electron from an atom.

Two cannon balls weighing 18 kg and 24 kg are chained together and fired horizontally with a velocity of 165 m/s from the top of a 21-m wall. the chain breaks during the flight of the cannonballs and the 18-kg cannonball strikes the ground at t = 1.5 s, at a distance of 240 m from the foot of the wall, and 7 m to the right of the line of fire. determine the position of the other cannonball at that instant. neglect the resistance of the air.