15) B

Think about this for a minute.

Infrared has a longer wavelength than ultraviolet. You can know this by looking at the electromagnetic radiation.

Since, frequency does not change during refraction and c ∝ λ , we can know that speed of red light would be higher than violet light in the air bubble.
This means that red light will refract less than violet light.

Let us use elimination now.

Both red and violet light will follow the same path after they exit the bubble. Hence, C and D are wrong.

Since the incidence occurs at the top half of the bubble, the refraction will also occur in the top half of the bubble. Hence, E and F are wrong.

Since red light will refract less than violet light, B is the answer.