Session 1, Page 5: Direction of Refraction


Light is refracted toward the normal when it passes from a less dense medium into a denser medium, as illustrated in Figure 6, because its velocity decreases. Conversely, light is refracted away from the normal when it passes from a dense medium into a less dense medium, as illustrated in Figure 7, because its velocity increases.

$refraction1.gif (4024 bytes)$ Figure 6 Incident ray passing into a denser medium is refracted toward the normal.	$refraction2.gif (3922 bytes)$ Figure 7 Incident ray passing into a less dense medium is refracted away from the normal.


When light passes through a substance with parallel surfaces, such as the pane of glass in Figure 8, the light will be refracted toward the normal at the first boundary, then refracted an equal amount away from the normal at the second boundary. The light ray that emerges will be parallel to its incident light ray but laterally displaced, or shifted. When light passes between any two mediums perpendicular to the boundary, the light is not bent either away from or toward the normal, but passes through without experiencing any refraction.	$refraction3.gif (4340 bytes)$ Figure 8 Light passing through a pane of glass or any other substance with parallel surfaces.

	Introduction to Solar Observing	Course Overview	Course Syllabus	Course Schedule
	Introduction to Solar Observing	Index of Course Sessions