An oxygen atom at a particular site within a dna molecule can be made to execute simple harmonic motion when illuminated by infrared light. the oxygen atom is bound with a spring-like chemical bond to a phosphorus atom, which is rigidly attached to the dna backbone. the oscillation of the oxygen atom occurs with frequency of=3.7×1013 hz.

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?