Special Relativity with 2 light beams moving towards each other

[Felipe Doria]

Homework Statement

If one light beam is heading toward you from the right, and another is heading toward you from the left, how quickly from the perspective of the right-moving beam is the left-moving beam approaching it?

1) 0
2) c
3) 1.5c
4) 2c

Homework Equations

(v+w) / (1 + cw/c2)

The Attempt at a Solution

I tried plugging in c into the equation for both v and w but it gives me (c + c) / (1 + c2/c2) which equals 2c. It is one of the possible answers but I know nothing can go faster than c so I'm thinking the answer is probably c. Am I right? If so, why? If not, what am I doing wrong?

 

[Dick]

Homework Statement

If one light beam is heading toward you from the right, and another is heading toward you from the left, how quickly from the perspective of the right-moving beam is the left-moving beam approaching it?

1) 0
2) c
3) 1.5c
4) 2c

Homework Equations

(v+w) / (1 + cw/c2)

The Attempt at a Solution

I tried plugging in c into the equation for both v and w but it gives me (c + c) / (1 + c2/c2) which equals 2c. It is one of the possible answers but I know nothing can go faster than c so I'm thinking the answer is probably c. Am I right? If so, why? If not, what am I doing wrong?

(c+c)/(1+c^2/c^2) isn't equal to 2c.