Question

If the distance between first maxima and fifth minima of a double slit pattern is 7 mm and the slits are separated by 0.15 mm with the screen 50 cm away, the wavelength of light used is:

• A. 200 nm
• B. 100 nm
• C. 800 nm
• D. 600 nm

Hint:

Carefully count fringe order when mixing maxima and minima.

Answer 1

The Correct Option is D

Step 1: Fringe width. β = (λ D)/(d)
Step 2: Distance relation. Distance between 1st maxima and 5th minima: x = (9)/(2)β
Step 3: Solving for wavelength. λ = (2xd)/(9D) = 600 nm