In the Young's double slit experiment, the interference pattern is found to have an intensity ratio between bright and dark fringes as 9. This implies that

ImaxImin=a1+a22a1−a22 Given that ImaxImin=9 a1+a22a1−a22=9  or  a1+a2a1−a2=3 or a1+a2=3a1−3a2  or  a1=2a2 Hence answer [d) is correct.  Let I1 and I2 be the intensities due to two slits. Then  I1∝a12 and I2∝a22 I1I2=a12a22=2a22a22=41 Hence aaswer (b) is correct