Question

4/10 what is the role of the normal line in refraction? it indicates the direction of the emergent ray it is parallel to the refracted ray it measures the intensity of the refracted ray it is perpendicular to the boundary at the point of

Explanation:

In the context of refraction, the normal line is a fundamental reference. It is a line that is perpendicular to the boundary (such as the interface between two media like air - water) at the point of incidence. It serves as a reference for measuring angles related to refraction, such as the angle of incidence and the angle of refraction.

• The first option is incorrect because the normal line does not indicate the direction of the emergent ray. The direction of the emergent ray is determined by the laws of refraction (Snell's law) which involve angles measured with respect to the normal.
• The second option is wrong. The refracted ray is not parallel to the normal. The refracted ray bends towards or away from the normal depending on the refractive indices of the two media.
• The third option is incorrect. The normal line has no role in measuring the intensity of the refracted ray. The intensity of the refracted ray is related to factors like the refractive indices of the media and the angle of incidence (to some extent through Fresnel's equations), but not the normal line.
• The fourth option is correct. By definition, the normal line is perpendicular to the boundary at the point of incidence.

Answer:

It is perpendicular to the boundary at the point of