Topic explanation

Standard explanation

For a diffraction grating, principal maxima occur when the path difference between waves from adjacent slits is an integer number of wavelengths.

Key points

• θ=0
• d sinθ=λ
• sinθ≤1
• nλ≤d
• Central Maximum: For slit spacing: d and diffraction angle: θ path difference between adjacent slit waves
• First Order: 0 **d sinθ=λ**
• A diffraction grating separates wavelengths because each wavelength has a different diffraction angle.

Labelled diagram