Chapter 22 - Reflection and Refraction of Light - Learning Path Questions and Exercises - Exercises - Page 774: 23

a). $(3)$ is the right answer. b). $\frac{15}{16}=0.9375$

a). $n=\frac{lambda_{vacuum}}{lambda_{m}}$ $n_{A}=1.33$ $n_{B}=1.25$ From above, it's clear that since the refractive index in medium A is greater than that of B, the wavelength in A will be less than that in B. (3) is the answer. b). Now, $\frac{lambda_{A}}{lambda_{B}}=\frac{n_{B}}{n_{A}}=\frac{1.25}{1.33}=\frac{15}{16}=0.9735$