"a student bikes to school by traveling first dn = 0.900" and "similarly, let d⃗ w be the displacement vector corresponding to the second leg of the student's trip. express d⃗ w in component form. express your answer as two numbers separated by a comma. be careful with your signs"

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?