# Energy of light

If a beam of light is travelling in full vacuum in same medium ,then , the energy of the light beam will decrease or not while moving through space ? The wavelength of the beam of light will change or not ?

Here below is a very rough sketch, consider the black square as being of the same size. Even though all of the energy in the wave is still very much in existence, the intensity on the square is lowered, $$\frac{W}{m^2}$$.