Theory of Interference Quiz

1. In this expression;

I = (a₁ – a₂)² + 4 a₁a₂ Cos² (δ/2);

a₁ and a₂ are constants, the intensity depends only on the constant phase difference value that is δ . Then intensity will be minimum if;

(a) Cos² (δ/2)= +2

(b) Cos δ = +1

(c) Cos δ = -1

(d) Cos δ/2 = -2

2. In the Principle of Superposition, mathematical expression where we explain the minima and maxima condition for the interference, we consider mathematical assumptions; one is

a₁ + a₂ Cosδ = A Cos Φ

what is the second one, select right one and give the answer.

(a) a₂ Sinδ = A Sin Φ

(b) a₁ + a₂ Sinδ = A Sin (Φ +δ)

(c) a₂ SinΦ = B Sin δ

(d) a₁ + a₂ Cosδ = A Cos (Φ +δ)

3. For bright fringe or maximum intensity at the centre (say O), the path difference must be an even multiple of the half-wavelength (λ/2) of light used. In a two slit experiment the distance of the n^th bright fringe from the point O will be;

(a)

(b)

(c)

(d)

4. The relationship between path difference and phase difference is;

(a) Path difference = 2λ/π x Phase difference

(b) Path difference = 2π/λ x Phase difference

(c) Phase difference = λ/2π x Path difference

(d) Path difference = λ/2π x Phase difference

5. The coherent sources whose intensity ratio is 81:1 produce interference fringes. Deduce the ratio of maximum intensity to minimum intensity in fringe system.

6. The resultant intensity of light at any point is

The avaerage intensity is solved as;

The average intensity result is ;

(a) I₁+I₂

(b)  I₁ – I₂

(c) I₁ x I₂

(d) I₁ / I₂

7. Angular Fringe Width

The angular fringe width is defined as the angular separation between consecutive bright or dark fringes.

Here tan θ = Fringe width / Distance

because this angle is very small so you can write;

θ=Fringe width / Distance

What will be the result for angular fringe width;

(a)

(b)

(c)

(d)

8. In this expression;

I = (a₁ – a₂)² + 4 a₁a₂ Cos² (δ/2);

a₁ and a₂ are constants, the intensity depends only on the constant phase difference value that is δ . Then intensity will be maximum if;

(a) Cos² (δ/2)= -1

(b) Cos δ = +1

(c) Cos δ = -1

(d) Cos δ/2 = +2

9. The distance of the n^th dark fringe from centre point O is;

(a)

(b)

(c)

(d)

10. A source is coherent if it satisfy the condition;