The dashed line represents the normal to the boundary
Explanation:
Refraction is a phenomenon that occurs when a ray of light crosses the interface between two mediums.
When this occurs, the ray of light changes direction and speed.
The new direction of the ray of light is given by Snell's law:
[tex]n_1 sin \theta_1 = n_2 sin \theta_2[/tex]
where
[tex]n_1[/tex] is the index of refraction of the 1st medium
[tex]n_2[/tex] is the index of refraction of thre 2nd medium
[tex]\theta_1[/tex] is the angle of incidence, which is the angle between the direction of the incident ray and the normal to the boundary
[tex]\theta_2[/tex] is the angle of refraction, which is the angle between the direction of the refracted ray and the normal to the boundary
The index of refraction of a medium is the ratio between the speed of light in a vacuum (c) and the speed of light in that medium (v):
[tex]n=\frac{c}{v}[/tex]
The figure in the question is missing, however you can find it in attachment.
We see that the dashed line is perpendicualr to the boundary between the two mediums, so it represents the normal.
So, the correct answer is
Normal
We note that in this case the ray of light bends towards the normal, this means that [tex]\theta_2<\theta_1[/tex], therefore the second medium has a larger index of refraction ([tex]n_2>n_1[/tex]).
Learn more about refraction:
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