How does distance from the slit affect the diffraction pattern?

The distance from the slit affects the diffraction pattern by altering the size and intensity of the pattern.

In more detail, diffraction is a wave phenomenon that occurs when a wave encounters an obstacle or a slit. The wave bends around the obstacle or passes through the slit and spreads out, creating a diffraction pattern. This pattern is characterised by a central bright fringe (maximum) surrounded by alternating dark and bright fringes (minima and maxima).

The distance from the slit to the screen where the diffraction pattern is observed plays a significant role in determining the size and intensity of the pattern. As the distance increases, the diffraction pattern expands, and the fringes become wider. This is because the diffracted waves have more space to spread out and interfere with each other. The central maximum becomes wider and the intensity of the light decreases as the light energy is spread over a larger area.

Conversely, if the distance from the slit to the screen decreases, the diffraction pattern contracts and the fringes become narrower. The central maximum becomes narrower and the intensity of the light increases as the light energy is concentrated in a smaller area.

The relationship between the distance from the slit and the size of the diffraction pattern can be quantified using the formula for single-slit diffraction: λ = wL/d, where λ is the wavelength of the light, w is the width of the central maximum, L is the distance from the slit to the screen, and d is the width of the slit. From this formula, it can be seen that as L increases, so does w, indicating a larger diffraction pattern.

IB Physics Tutor Summary: In simpler terms, the distance from the slit to where we see the diffraction pattern changes its size and brightness. When this distance gets bigger, the pattern spreads out more, making the light fringes wider and less bright. A shorter distance does the opposite, making the pattern tighter and brighter. This is because of how light waves spread and mix together.