Answer:
its 30 i did this homeweok
Explanation:
30
<span>The fact that light travels at 300,000 km/s is a consequence of Energy Conservation
The particle that move with that kind of speed creates energy way faster than the particle that don't. Which means that it would require less effort to produce the energy,</span>
The basic relationship between frequency of an electromagnetic wave and wavelength of the wave is

where

is the speed of light.
Manipulating the equation, we can rewrite it as

The frequency of the wave in our problem is

so if we use the previous formula, we find the correspondant wavelength: