The mass of a star can be determined by studying
a. the wavelength of light emitted by the star.
b. the color of the star.
c. kepler's laws.
d. binary star systems.

Which is not true about oxygen-17 and oxygen-18?

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?

In which of these cases are the two wave points considered to be in phase with each other?