A wood block has a mass of 1000g and is 65% submerged under water, of its total volume. What is the density of the wood? How much weight will be needed on top of the wood block in order for it to be 100% submerged under water? Density of water is 997 kg/m3.

Amichelson interferometer operating at a 600 nm wavelength has a 3.02-cm-long glass cell in one arm. to begin, the air is pumped out of the cell and mirror m2 is adjusted to produce a bright spot at the center of the interference pattern. then a valve is opened and air is slowly admitted into the cell. the index of refraction of air at 1.00 atm pressure is 1.00028.how many bright-dark-bright fringe shifts are observed as the cell fills with air?