What is diffraction?

When is diffraction most noticeable?

State the Fresnel number used to classify diffraction regimes.

What regime is usually associated with \(N_F\ll1\)?

What regime is usually associated with \(N_F\gtrsim1\)?

A slit has \(a=0.20\,\mathrm{mm}\), \(L=2.0\,\mathrm{m}\), and \(\lambda=500\,\mathrm{nm}\). Find \(N_F\).

A slit has \(a=1.0\,\mathrm{mm}\), \(L=0.50\,\mathrm{m}\), and \(\lambda=500\,\mathrm{nm}\). Find \(N_F\).

How does increasing the screen distance \(L\) affect the Fresnel number?

How does increasing aperture width \(a\) affect the Fresnel number?

For a far-field diffraction pattern, what small-angle relation connects screen position and angle?

A diffraction feature is observed at \(y=4.0\,\mathrm{mm}\) on a screen \(2.0\,\mathrm{m}\) away. Estimate \(\theta\).

Why are Fraunhofer diffraction patterns often described as angular patterns?

Why is a lens often used to observe Fraunhofer diffraction in a laboratory?

A setup has \(N_F=0.02\). Should wavefront curvature near the aperture be a dominant part of the observed pattern?

Find the screen distance needed for \(N_F=1\) when \(a=0.50\,\mathrm{mm}\) and \(\lambda=500\,\mathrm{nm}\).

If the wavelength is doubled with \(a\) and \(L\) fixed, what happens to \(N_F\)?

Explain why geometric optics fails when a slit is very narrow compared with the beam size but comparable with the wavelength.

Two setups use the same aperture and wavelength. Setup A has \(L=1.0\,\mathrm{m}\), and setup B has \(L=4.0\,\mathrm{m}\). Compare their Fresnel numbers.

A pattern is first described by angle \(\theta\), then plotted on a screen. What assumption is needed to use \(y\approx L\theta\)?

A slit width is chosen so that \(N_F=1\). Express \(a\) in terms of \(\lambda\) and \(L\).