# What are the dimensions of huygen wavelets

According to Wikipedia the formula for the field created by an aperture (the Kirchoff-Fresnel Integral) is:

$$\Psi(r)\propto \int\!\!\!\int_\mathrm{aperture} E_{inc}(x',y')~ \frac{e^{ik | \bold r - \bold r'|}}{4 \pi | \bold r - \bold r' |} \,dx'\, dy',$$

http://en.wikipedia.org/wiki/Huygen's_principle#Diffraction_by_a_general_aperture

How do the units work out for this? The right hand side has units of electric field times length, so don't we need to get rid of the length somehow? The only thing I can think of is to divide by the wavelength, but if that's the case, then they would have added it to the right hand side to emphasize it, because that seems important. The wavelength can already appear in equations due to the k in the integral.