Question

nth bright fringe if red light `(lambda_(1)=7500" Å")` coincides with (n +1)th bright fringe of green light `(lambda_(2)=6000" Å")` The value of n, is
A. 4
B. 5
C. 3
D. 2

Answer 1

Correct Answer - A
Since, the two bright fringes coincide
`therefore nlambda_(1)=(n+1)lambda_(2)`
`or (n+1)/(n)=(lambda_(1))/(lambda_(2))=(7500)/(60000)=(5)/(4)`
`or 1+(1)/(n)=(5)/(4) rArr n=4`