Physics

Physics

Problem

Light of wavelength 500 nm500\,\text{nm} is incident normally on a diffraction grating ruled with 600 lines mm−1600\,\text{lines\,mm}^{-1}. Calculate the diffraction angle at which the second–order (m=2m=2) bright fringe is observed. Give your answer in degrees.
Intuitive explanation

The key is recognizing that a diffraction grating creates bright fringes when light from adjacent slits interferes constructively—which happens when the path difference equals an integer multiple of the wavelength. You'll use the grating equation dsin⁡θ=mλd\sin\theta = m\lambda to connect the slit spacing dd (found from the line density), the wavelength, and the order mm to find the angle. Just be careful to convert units consistently before plugging in numbers.

Intuitive explanation

The key is recognizing that a diffraction grating creates bright fringes when light from adjacent slits interferes constructively—which happens when the path difference equals an integer multiple of the wavelength. You'll use the grating equation dsin⁡θ=mλd\sin\theta = m\lambda to connect the slit spacing dd (found from the line density), the wavelength, and the order mm to find the angle. Just be careful to convert units consistently before plugging in numbers.

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