The difference of speed of light in the two media A and B (v
A
$- v
B
) is 2.6 \times 10
7
m/s. If the refractive index of medium B is 1.47, then the ratio of refractive index of medium B to medium A is : (Given : speed of light in vacuum c = 3 \times 10
8
ms
-$1
)