Question

To obtain the central maximum at the centre, a mica sheet of refractive index 1.5 is introduced. Which of the following is correct ?

• A. The thickness of sheet is 2($\sqrt{2}$–1)d in front of S₁
• B. The thickness of sheet ($\sqrt{2}$+1)d in front of S₂
• C. The thickness of sheet is (2$\sqrt{2}$ d –1) in front of S₂
• D. The thickness of sheet is (2$\sqrt{2}$–1)d in front of S₁

Answer 1

Answer: (A)

The thickness of sheet is 2($\sqrt{2}$–1)d in front of S₁

Answer 2

Path different

$\sqrt{2}$d – d = (m _ 1) t

d ($\sqrt{2}$ – 1) = (1.5 – 1) t

t = 2($\sqrt{2}$ – 1) d