| Light Ray: To place a light ray, click on a light source, then drag out the ray in the direction and to the length you desire. To move the light ray along the light source (other than a point source), select the ray and drag it vertically along the source. You can also use the up and down arrow keys to move the ray one pixel at a time. To extend or contract a ray and change its direction, select the ray. Then click on the "hot spot" on the arrowhead and drag the ray to the desired length and direction. Light rays only follow actual light paths in Run mode. In a ray's Properties Box, you can change the ray's color. You can choose to show the backward extension of refracted and reflected rays . This option shows the apparent location of the light source to observers). The backward extensions are gray and colinear with the reflected or refracted rays. You can also show total reflection at two-media interfaces where refraction occurs (for example, air and water). Reflected rays are gray (same shade as the backward extensions), while refracted rays retain the original ray color. The simulator does not calculate any additional reflections or refractions of gray reflected rays. For both options above, you can choose to show total reflection (backward extensions) at only the first refracting/reflecting surface, the last refracting/reflecting surface, or all refracting/reflecting surfaces encountered by the ray. Note: If reflection is complete (no refraction occurs) at a two-media interface, the simulator will display the reflection with the total reflection feature turned off.