Answer:
7.55 * 10^(-5) m
Explanation:
Parameters given:
Wavelength of light, λ = 381 nm = 3.81 * 10^(-7) m
Distance between screen and slit, L = 85 cm = 0.85 m
Distance of the first-order dark band from the center of the pattern, x = 0.43cm = 0.0043 m
The relationship between λ, L, x and the width of the slit, w is given as:
λ/w = x/L
=> w = λL/x
w = (3.81 * 10^(-7) * 0.85)/(0.0043)
w = 7.55 * 10^(-5) m