Optics Question 474
Question: In a YDSE bichromatic lights of wavelengths 400 nm and 560 nm are used. The distance between the slits is 0.1 mm and the distance between the plane of the slits and the screen is 1 m. The minimum distance between two successive regions of complete darkness is
Options:
A) 4 mm
B) 5.6 mm
C) 14 mm
D) 28 mm
Show Answer
Answer:
Correct Answer: D
Solution:
[d] Let nth minima of 400 nm coincides with nth minima of 560 nm then
$ (2n-1)400=(2m-1)560\Rightarrow \frac{2n-1}{2m-1}=\frac{7}{5}=\frac{14}{10}=\frac{21}{15} $
i.e., 4th minima of 400 nm coincides with 3rd minima of 560 nm.
The location of this minima is $ =\frac{21(1000)(4000\times {{10}^{-6}})}{2\times 0.1}=42mm $
$ \therefore $ Required distance=28mm
