How can lasers be utilised in single-slit experiments?

Lasers can be utilised in single-slit experiments to produce and study diffraction and interference patterns.

In a single-slit experiment, a laser beam is directed towards a narrow slit. The laser light, being monochromatic and coherent, is ideal for this experiment as it ensures that the light waves are in phase and of the same wavelength. When the laser light passes through the slit, it diffracts, spreading out in a pattern that can be projected onto a screen.

The pattern observed on the screen is a result of the superposition of the light waves, which interfere with each other. In the centre of the pattern, constructive interference occurs where the waves combine to form a bright central maximum. On either side of this central maximum, there are alternating dark and bright fringes. The dark fringes are a result of destructive interference, where the waves cancel each other out, while the bright fringes are due to constructive interference.

The width of the central maximum and the spacing between the fringes can be used to calculate the wavelength of the laser light. This is done using the formula for single-slit diffraction, which relates the wavelength of the light, the width of the slit, and the angle to the position of the fringes on the screen. By measuring the distance from the central maximum to the first dark fringe, and knowing the distance from the slit to the screen, the angle can be calculated. This can then be used to find the wavelength of the laser light.

In addition to determining the wavelength of light, single-slit experiments with lasers can also be used to study the principles of wave-particle duality. This is a fundamental concept in quantum mechanics, which states that particles such as photons can exhibit both wave-like and particle-like properties. The diffraction and interference patterns observed in the single-slit experiment demonstrate the wave-like nature of light, while the detection of individual photons on the screen shows its particle-like nature.