Question

Two coherent sources of equal intensity produce maximum intensity of `100` units at a point. If the intensity of one of the sources is reduced by 36% reducing its width, then the intensity of light at the same point will be
A. (a) 90
B. (b) 89
C. (c) 67
D. (d) 81

Answer 1

Correct Answer - D
Intensity of each source `=I_0=(100)/(4)=25unit`
If the intensity of one of the source is reduced by 36% then `I_1=25unit` and
`I_2=25-25xx(36)/(100)=16(unit)`
Hence resultant inensity at the same point will be
`I=I_1+I_2+2sqrt(I_1I_2)=25+16+2sqrt(25xx16)=81unit`