The collimated parallel beam of a LASER

[Asmaa Mohammad]

Homework Statement

Multiple-choice question:
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!

 

[TSny]

https://en.wikipedia.org/wiki/Collimated_light
What has more emphasis here, direction or phase?

 

[mfb]

You can collimate the light of every light source.

It depends on how you pronounce the sentence I guess. If you highlight laser, then the phase is the important point, if you highlight collimated parallel beam (more natural I think), then it is the direction.

 

[Asmaa Mohammad]

https://en.wikipedia.org/wiki/Collimated_light
What has more emphasis here, direction or phase?

I think it is the direction, right?

You can collimate the light of every light source.

It depends on how you pronounce the sentence I guess. If you highlight laser, then the phase is the important point, if you highlight collimated parallel beam (more natural I think), then it is the direction.

I study LASER in my course, and by studying it I came to the concept of "collimated parallel beam". So, which choice would be more suitable for this question?

 

[mfb]

I would pick direction. If the format allows it, add a comment that the coherence in phase is given by the fact that it is a laser beam.