Question

Violet light (λ = 400 nm) passing through a diffraction grating for which the slit spacing is 6.0 μm forms a pattern on a screen 1.0 m away from the grating. Part A Is the fringe located at a linear distance y = 204 mm to the left of the central bright fringe a bright fringe, a dark fringe, or something in between? What is the order of the fringe?

Answer 1

Answer:

3 order dark fringe

Explanation:

y = Distance from central bright fringe = 204 mm

λ = Wavelength = 400 nm

L = Distance between screen and source = 1 m

d = Slit distance = 6 μm

$tan\theta =\frac{y}{L}\\\Rightarrow tan\theta =\frac{204}{1000}=0.2012^{\circ}$

$dsin\theta=m\lambda\\\Rightarrow m=\frac{dsin\theta}{\lambda}\\\Rightarrow m=\frac{6\times 10^{-6}sin0.2012}{400\times 10^{-9}}=2.9982\approx 3$

Order of fringe is 3

So, it is a Dark order fringe