fix size of heading #263

doc/model.md

@@ -3,20 +3,20 @@
 This is a high-level description of the model used in Wave Interference. It's intended for audiences
 that are not necessarily technical.
 
-# Waves Screen
+## Waves Screen
 
 This screen depicts a 2D wave on the surface of water, or the cross-section of a spherical wave for sound or light. The
 user can choose between a continuous or pulse wave.  The user can control the frequency and amplitude of the wave,
 and observe how it appears on the center line in a chart.  For light, the user can also observe the light collecting
 on the screen on the right.  The wave speeds can be computed as `wave speed = frequency * wavelength`.
 
-# Interference Screen
+## Interference Screen
 
 This screen has two point sources that can be enabled/disabled independently, and interference patterns emerge from the
 overlapping waves.  The point sources are always in-phase.  The interference pattern shows constructive interference
 at `d * sin(theta) = m * lambda`.
 
-# Slits Screen
+## Slits Screen
 
 This screen provides an incoming plane wave, and the user can control the location of the barrier, the number of
 slits and the location and width of the slits.  According to the Huygens-Fresnel principle, each part of the wave
@@ -34,6 +34,6 @@ For single slit (where `a` is the width of the aperture):
 
 see http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/sinslit.html
 
-# Diffraction Screen (under development)
+## Diffraction Screen (under development)
 
 The diffraction pattern is computed as the discrete Fast Fourier Transform of the input pattern.