# Slit width order of wavelength

1. Feb 22, 2012

### jd12345

In diffraction why the slit width has to be the order of wavelength of wave? I dont understand. The smaller the width of the slit i think the more effective diffraction becomes.
Why the width has to be order of the wavelength?

2. Feb 24, 2012

### Claude Bile

It doesn't. It can be much smaller or much larger. Diffraction theory can easily account for both.

Look up "Kirchoff integral theorem".

Claude.