In vacuum the speed of light is c 299792458 x 10 8 ms This vacuum speed of light c is what the statements from relativity describe. We know exactly what the speed of light is. Measuring the Speed of Light from Astronomical Observations.
The speed of light could then be found by dividing the diameter of the Earths orbit by the time difference.
If you want to determine the wavelength of light given the specific energy of a photon you would use the energy equation. The formula for average speed also called average velocity in physics and engineering is. You will need two light bulbs 800 lumens each to illuminate the whole kitchen and additional 7 LED lights 200 lumens each above the counter. 10-34 Js and mass of proton m16726231.