a. A transparent slab P is placed in contact with another slab Q. The absolute refractive index of Q is 1.60 and the relative refractive index of P with respect to Q is 1.20. Calculate the absolute refractive index of P.
b. Determine the relative refractive index of Q with respect to P and show that the product of the two relative refractive indices obtained in parts (i) and (ii) equals 1.