What is mantle convection?
a. cool matter rises and heats up and then falls and cools again and again, sometimes it will be erupted out of volcanoes
b. cool matter falls and heats up and rises and cools again and again, sometimes it will erupt out of volcanoes
c. cool matter rises and cools even more and then falls and heats up again and again, sometimes erupting from volcanoes

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?