Question

If one of the two slits of a Young's double slit experiment is painted over so that it transmits half the light intensity of the other, then –

• A. The fringe system would disappear
• B. The bright fringes will be more bright & dark fringes will be more dark
• C. The dark fringes would be bright and bright fringes would be darker
• D. Bright as well as dark fringes would be darker

Answer 1

Answer: (C)

The dark fringes would be bright and bright fringes would be darker

Answer 2

Let I₁ = a², I₂ = b²

\ $\frac{I_{\max}}{I_{\min}}$=$\frac{(a + b)^{2}}{(a - b)^{2}}$ and $\frac{I_{\max}^{'}}{I_{\min}^{'}}$=$\frac{\left( \frac{a + b}{\sqrt{2}} \right)^{2}}{\left( \frac{a - b}{\sqrt{2}} \right)^{2}}$

Comparing them, we get $I_{\max}^{'}$ < I_max; $I_{\min}^{'}$> I_min

Therefore the answer is (3).