What is the Relative Speed of Light at an Angle?

[Gear300]

Let us say that an observer, O, saw a ray of light, such as a laser light (yellow curve), pass at an angle (omega). The speed of light would be constant in all frames, but wouldn't the observer record a relative speed of light c' = c*cos(omega) -- orange line -- assuming he/she couldn't tell the intensity decrease?

 

[Ich]

c' is a component of the velocity. You get the velocity vector if you add the perpendicular component (which you omitted) to it. The length of this vector is called speed.

 

[Gear300]

Alright...Thanks for the reply.