Diffraction gratings are commonly used instead of single slits or double slits to measure the wavelength of light due to several advantages they offer:
High Angular Dispersion: Diffraction gratings provide a higher angular dispersion compared to single slits or double slits. Angular dispersion refers to the spreading out of different wavelengths of light at different angles. This property allows for better separation and measurement of different wavelengths, making it easier to determine the precise wavelength of light.
Multiple Slit Patterns: Diffraction gratings consist of a large number of equally spaced parallel slits. The presence of multiple slits enhances the intensity of the diffracted light and provides more well-defined interference patterns. This results in sharper and more distinct fringes, making it easier to accurately measure the positions of maxima and minima.
Greater Accuracy: The precise spacing between the slits in a diffraction grating is known with a high degree of accuracy. This information is crucial for determining the wavelength of light using the grating equation: nλ = d(sinθᵢ + sinθₒ), where n is the order of the interference, λ is the wavelength of light, d is the grating spacing, θᵢ is the incident angle, and θₒ is the diffracted angle. The accurately known spacing of the grating allows for more precise calculations of the wavelength.
Wider Range of Wavelengths: Diffraction gratings can be manufactured with various spacings to suit different ranges of wavelengths. By selecting a grating with an appropriate spacing, it is possible to measure a wide range of wavelengths accurately. This flexibility makes diffraction gratings versatile for various applications in spectroscopy and wavelength measurement.
Overall, the use of diffraction gratings provides better angular dispersion, higher accuracy, well-defined interference patterns, and a wider range of measurable wavelengths compared to single slits or double slits, making them a preferred choice for measuring the wavelength of light.