FORMATION OF SHADOWS LABORATORY EXERCISE 3 PHYSICS Introduction

FORMATION OF SHADOWS LABORATORY EXERCISE 3 PHYSICS

Introduction • When light shines on an object, some of the rays may be stopped while others pass on in a straightline path forming a shadow where light rays cannot reach. If you look at a shadow, you notice that there is a dark central region and a fuzzy and less dark band around the edge of the central region. Why do shadows have different regions?

Materials • Bright light source • Book or other opaque material • Screen wall • Meter stick

Procedures • 1. Arrange a small light source so that a solid object such as a book casts a shadow on a screen or wall, Sketch the shadow formed, noting both its regions. Sketch the relative positions of the book light source and shadow

• 2. Move the light source away from the object while keeping the position of the object fixed. Not and sketch any changes in the shadow. Sketch the new relative position of the light source

• What happens to the size of the fuzzy region around the edge of the region when the light source is moved a further away? Fuzzy region around the edge becomes narrower

3. Move the object closer to the light source while keeping the screen and the light source in the same position. Note and sketch any changes in the shadow. Sketch the new relative position of the object

• What happens to the size of the fuzzy region around the edge of the region when the object is moved closer to the light source? Fuzzy region around the edge becomes wider/fuzzier

Analysis Questions • 1. Which relative positions of the object, light source, and the screen result in a sharper distinct shadow with little or no fuzzy region around its edge? When the distance from the light source to the object is much greater than the distance from the object to the screen.

• 2. Which relative positions of the object, light source, and the screen result in a large fuzzy region around a small or nonexistent central dark? When the distance from the light source to the object is less than the distance from the object to the screen; large fuzziness occurs… dark region may disappear.

• 3. What causes fuzzy region around the edge of a shadow? The fuzzy region exists where the light source is partially blocked by the object. Its size depends on the relative size of the light source and the object as well as the distance between the light source and object compared to that between the object and the screen.