Eli5: If light has no mass, how does it gain momentum / have energy / reflect off a mirror?

1.40K views

Is it 100% confirmed that light has no mass? Because if it has mass the titled questions should be easier to answer the observed behaviour of light. Right? Or I’m way off… pls.

In: Physics

2 Answers

Anonymous 0 Comments

Momentum is not exclusive to moving mass. The usual equation L = m*v is a special case for massive objects.

Waves carry momentum without actual net-movement of mass. This applies both to mechanical waves (where there is moving mass, but its average velocity is zero) and electromagnetic waves (which have no mass). The wave-part is simply negligibly small in most applications.

Cant explain the details of how exactly light obtains momentum, thats beyond me.

You are viewing 1 out of 2 answers, click here to view all answers.