Question Detail
Question
Monochromatic light from a laser passes through two slits separated by 0.005 mm. The third bright line on a screen is formed at an angle of 18° relative to the incident beam. What is the wavelength of the light?
Correct Answer
Option C is the correct answer.
Detailed Explanation
For bright fringes: d sin θ = mλ. d = 0.005 mm = 5 × 10⁻⁶ m, m = 3, θ = 18°. λ = d sin θ / m = (5e-6 × sin 18°) / 3 = (5e-6 × 0.3090) / 3 = 1.545e-6 / 3 = 5.15 × 10⁻⁷ m = 515 nm.
Hint
Use d sin θ = mλ.