Question

To prevent reflection from a camera lens, a thin film of magnesium is coated. In order that the light of wavelength 5000 Å not be reflected the minimum thickness of the film should be (m for magnesium = 1.25 and m for glass = 1.5) –

• A. 2 × 10^–7m
• B. 10^–7 m
• C. 2 × 10^–6m
• D. 2 × 10^–8 m

Answer 1

Answer: (B)

10^–7 m

Answer 2

2mt = $\frac{\lambda}{2}$ condition for distructive interference