# Parameter definitions for "huygens"

The program simulates the wave propagation through vertical slits (along the Z axis) in a screen at X=0. There are two outputs displayed: a grey-scale ``wave tank'' view of the wave amplitude in the XY plane (default 10m by 10m), and the wave average intensity (or alternatively the instantaneous amplitude) at a screen at large X (default distance 100m).

There are two sliders for setting the properties of the waves:

• Lambda sets the wavelength of the wave in meters, and
• Phase sets the phase of the light incident as it passes through the slits.
There are two sliders for setting the properties of the slits:
• d sets the overall height of the array of slits, in meters. If there is only one slit, d is irrelevant; if there are two slits, it gives the distance between their centers. If there are more than two slits, it gives the distance between the centers of the bottom-most and top-most slit. For more than two slits, it does NOT give the distance between centers of neighboring slits.
• a gives the width of the slits in meters. Since we're often interested in slits of very small width, we treat a=0 in a special way. Of course, a slit of zero width should let in no waves! Instead, for a=0 we make the intensity of the waves equal to Amplitude Per Point Source (described under Configure below).
There is a button, a menu, and a text input to control the graph.
• copy graph button to the right of the graph selection menu allows you to capture a plot; you can then combine plots, print plots, save plots, ...
• intensity/amplitude menu lets you look at the average intensity incident on the screen, or the instantaneous amplitude of the wave at the screen.