Optics - Wave Optics - SS2 Physics Past Questions and Answers - page 2

Young's double-slit experiment is a fundamental experiment in the field of wave optics that provides compelling evidence for the wave-particle duality of light. The experiment consists of a light source, a barrier with two closely spaced slits, and a screen placed behind the barrier to observe the interference pattern.

When light from a single source passes through the double slits, it diffracts and creates two coherent wavefronts that propagate outward. These wavefronts then overlap and interfere with each other when they reach the screen. The interference pattern appears as a series of bright and dark fringes on the screen.

The key observation of the experiment is the presence of interference fringes, which can only be explained if we consider light as a wave phenomenon. The bright fringes correspond to constructive interference, where the peaks of the two wavefronts align, resulting in an increased intensity of light. The dark fringes, on the other hand, correspond to destructive interference, where the peaks of one wavefront align with the troughs of the other, resulting in a cancellation of light.

The implications of Young's double-slit experiment on the wave-particle duality of light are profound. Initially, light was believed to be purely a wave phenomenon. However, the observation of interference fringes challenges this notion. To explain the experiment's results, it was proposed that light must also exhibit particle-like behaviour.

According to the wave-particle duality principle, light can behave as both a wave and a particle, known as photons. The interference pattern in the double-slit experiment suggests that individual photons pass through both slits and interfere with themselves, leading to the observed fringes on the screen.

This experiment demonstrates that the behaviour of light depends on the conditions of observation. When observed collectively, light exhibits wave-like properties, such as interference. However, when observed individually, light behaves as discrete particles, photons, which explain the appearance of the interference pattern.

The implications of Young's double-slit experiment extend beyond light and have significant consequences for our understanding of quantum mechanics. Similar experiments have been conducted with electrons, demonstrating the wave-particle duality of matter as well.