Light and Optics

2	Light and Shadows

2.1 INTRODUCTION

To cast a shadow, we need light from a concentrated source, such as the Sun during the day or the Moon at night. A shadow is also cast by light that comes from a point source, which gives parallel light rays. Consider a flat white screen located a short distance away from the light source and an object placed between the screen and the light source. Part of the light rays are blocked by the object making a dark area, and part of the rays that reach the screen make that part of the screen bright. The dark area is called shadow. The shadow’s location can be figured out by drawing straight lines from the point ...