A disabled sailboat is drifting on a current that is moving at 3 miles per hour. Fortunately, it's drifting towards a Coast Guard station 47 miles away, which picks up the distress call and sends a rescue craft directly towards the sailboat. The rescue craft can travel 40 miles per hour. How long will it be before the two vessels meet?

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?