g A beam of light is traveling inside a solid glass cube that has index of refraction 1.68. It strikes the surface of the cube from the inside. Part A If the cube is in air, at what minimum angle with the normal inside the glass will this light not enter the air at this surface?

A47.2 g block of copper whose temperature is 480 k is placed in an insulating box with a 91.8 g block of lead whose temperature is 200 k. (a) what is the equilibrium temperature of the two-block system? (b) what is the change in the internal energy of the two-block system between the initial state and the equilibrium state? (c) what is the change in the entropy of the two-block system? the heat capacities of copper and lead are 386 j/kg·k and 128 j/kg·k, respectively.