CBSE Class 12 Physics 2020 Outside Delhi Set 1 Paper

Question : 33

Total: 37

Two coherent light waves of intensity 5× 10−2Wm−2 each superimpose and produce the interference pattern on a screen. At a point where the path difference between the waves is ‌

,λ being wavelength of the wave, find the
(a) phase difference between the waves
(b) resultant intensity at the point
(c) resultant intensity in terms of the intensity at the maximum

Solution:

(a) ∆x=‌

λ∆ϕ

2π

, where ∆x= Path difference and
‌∆ϕ=‌ Phase difference ‌
‌∆x=‌

‌∴∆ϕ=‌ phase difference ‌ =‌

×‌

2π

=‌

2π

(b) Resultant intensity =I=I0cos2‌

∆ϕ

‌ Or, ‌‌I=I0cos2‌

‌ Or, ‌‌I=5×10−2cos2‌

‌ Or, ‌‌I=5×10−2(‌

√3

)2
∴‌I=3.75×10−2Wm−2
(c) Resultant intensity at maxima =Imax=4I0
Resultant intensity =I‌RESULTANT ‌=‌

3l0

3I0

‌

I‌RESULTANT ‌

I‌MAX ‌

=‌

3I0∕4

4I0

=‌

∴I‌RESULTANT ‌=‌

I‌MAX ‌

Go to Question:

Prev Question

Next Question