The LASER beam is a collimated parallel one, that means that its photons have the same.......
(i) phase (ii) direction (iii) intensity (iv) frequency
Attempt at a solution
I would exclude frequency because it has nothing to do with the fact that LASER beam propagates as collimated beam. I would also exclude intensity too because...I don't know actually, but I don't think it is the correct answer.
But both the direction and the phase are good reasons why LASER propagates as a collimated parallel beam, but I should choose only one, so please help me!