# Intensity of waves in single-slit diffraction

So I am trying to determine the relation between intensities of waves in single slit diffraction. Since I am pretty new to this topic, I couldn't find a way how to calculate the ratio between the intensities of the source wave and central maxima. I have found how to calculate the ratio between the intensity of the central maxima and surrounding maxima. However, I see there is no source that can help me to determine the relation between the intensity of the source wave and central maxima.

Thus, let's say we have a plate with a single slit whose width is $\lambda_1$ $\mu m$ and we send a light beam with wavelength $\lambda_2$ $\mu m$ towards this plate from a source which is $x_1$ $m$ away from the plate. Moreover, we have a screen which is $x_2$ $m$ away from the plate. If we say that the intensity of the source wave is $I$, then what would be the intensity of the central maxima in terms of $I$? I also think this can be answered by calculating the total energies of waves but since it is an electromagnetic wave, I think the calculations may get harder.

P.S: The source is point-like and the slit is circular so we expect an airy disk pattern.

• You can look this up easily enough at, e.g. en.wikipedia.org/wiki/Diffraction#Single-slit_diffraction – Carl Witthoft Feb 18 '15 at 18:14
• @FarStar you give too few details about the configuration of your problem. Is your source point-like? Then the intensity of the wave decreases with the distance $r$ from the source as $1/(4pi r^2)$. Is the slit circular or a long slit of the mentioned width? – Sofia Feb 19 '15 at 0:01
• @CarlWitthoft I believe that equation gives the relation between the intensities of central maxima and other maximas not the intensities of central maxima and source. – user57144 Feb 19 '15 at 11:35
• @Sofia Yes the source is point-like and the slit is circular so we expect an airy disk pattern on the screen. – user57144 Feb 19 '15 at 11:37
• @FarStar Intensity of light from the source at the slit opening? – user35122 Feb 19 '15 at 16:38