Correct Answer - C
Wavelength of light in `X=(lambda)/(1.5)`, in `Y=(lambda)/(mu)`, in `Z=(lambda)/(1.6)`
Number of wavelegnth in X=number of wavelengths in Y+ number of wavelengths in Z
`(t)/(lambda//1.5)=(t//3)/(lambda//mu)+(2t//3)/(lambda//1.6)`
`1.5=mu/3+(3.2)/(3)impliesmu/3=1.5-(3.2)/(3)=(1.3)/(3)impliesmu=1.3`