A ray of light propagating through medium A enters another medium B such that the angle of incidence and angle of refraction are α and β. Given that sin α = \(({1\over x})\) and sin β = \(({1\over y})\), the refractive index of medium A with respect to medium B is
1
\(x\over y\)
2
\(y\over x\)
3
xy
4
\(1\over xy\)