A single slits of width 0.1 mm is illuminated by parallel light of wav...
Calculation of the Distance of the Third Dark Band from the Central Bright Band in Diffraction
Given data:
- Width of the single slit, w = 0.1 mm
- Wavelength of the incident light, λ = 6000 Å (6000 x 10^-10 m)
- Distance between the slit and the screen, D = 40 cm = 400 mm
To find: Distance of the third dark band from the central bright band
1. Calculation of Angular Position of the Third Dark Band:
- The angular position of the nth dark band is given by the formula:
sinθ ≈ nλ/w
- For the third dark band, n = 3.
- Rearranging the formula, we get:
θ ≈ sin^(-1)(nλ/w)
- Substituting the values, we have:
θ ≈ sin^(-1)((3 x 6000 x 10^-10 m)/(0.1 x 10^-3 m))
θ ≈ sin^(-1)(0.018)
- Using the small angle approximation, sinθ ≈ θ (for small values of θ):
θ ≈ 0.018
2. Calculation of Distance of the Third Dark Band:
- The distance between consecutive dark or bright bands on the screen can be found using the formula:
y = D x tanθ
- For the third dark band, we substitute θ = 0.018 and D = 400 mm:
y = 400 mm x tan(0.018)
y ≈ 7.2 mm
Therefore, the distance of the third dark band from the central bright band is approximately 7.2 mm.