Solving for Power & Speed: A Homework Challenge

[reallydumb]

Homework Statement

Every 2km power is reduced by half. Initial power = 10watt. What is power after traveled 8km?

C = 3x10⁸. What is speed of light passing through optic fibre? n = 1.55

Homework Equations

P = $$\frac{w}{T}$$ ?

The Attempt at a Solution

I don't know where to start

 

[ƒ(x)]

Write a formula relating power and distance.....

Spoiler

P = 10(2^-km/2)