Given:
A light beam strikes the surface of the water, it refracts toward the normal.
To find:
A diagram showing a light beam refracting towards the normal.
Explanation:
Let us call the medium in white color (air) medium 1 and the medium in gray color (water) medium 2.
The light ray that falls on the water surface is known as an incident ray. Whenever a light ray passes from a rarer medium to a denser medium, the light ray bends towards the normal. Here, medium 1 (air) is the rarer medium and medium 2 (water) is the denser medium. Thus, the refracted light ray will bend towards the normal.
The vertical dash line which is perpendicular to the water surface is known as a normal. In the given options, we see that, in option B, the refracted ray ( light ray in medium 2 of gray color) is bent towards the normal.
While, in option A, the refracted light ray is away from the normal.
In option C, the light ray is passing straight through medium 2. Thus it cannot be regarded as it is bending toward normal nor it is bending it away from the normal.
In option D, the light ray is reflected from the water surface. Thus it is a reflected ray and not a refracted ray.
Conclusion:
The correct option is option B. It shows the a light beam