The intensity of light from a continuously emitting laser source operating at 638 nm wavelength is modulated at 1 GHz . The modulation is done by momentarily cutting the intensity off with a frequency of 1 GHz . What is the farthest distance apart two detectors can be placed in the line of the laser light so that they can see the portions of the same pulse simultaneously ? ( consider the speed of light in air `3 xx 10^8 m//s` )

Options

A. 30 `mu`m
B. 30 cm
C. 3 m
D. 30 m