Vernier Software & Technology

# Interference

## Introduction

As long ago as the 17th century, there were two competing models to describe the nature of light. Isaac Newton believed that light was composed of particles, whereas Christopher Huygens viewed light as a series of waves. Both models could explain reflection and refraction, but the phenomena of diffraction and interference could be more easily explained by Huygens’ wave model. In the early 19th century, Thomas Young’s double-slit experiment provided evidence that supported the wave nature of light. This is the first of two experiments that examine the related phenomena of diffraction and interference. You will first compare the patterns that are produced when laser light passes through one or two slits and then strikes a screen. You will then focus your attention on the analysis of the double-slit interference pattern.

## Objectives

In this experiment, you will

• Compare and contrast features of the patterns produced on a screen when light from a laser passes through either one or two slits.
• Discern which features of the pattern arise from the interaction of the light with the single slit and which arise from the double slits.
• Use the principle of superposition to explain how waves from two sources could interfere constructively or destructively.
• Use a diagrammatic explanation of how path length differences for light passing through the two slits give rise to bright and dark fringes in the pattern.
• From experimental parameters, predict the spacing between bright (or dark) fringes in the pattern.
• Collect intensity vs. position data to test your predictions.

## Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

You may also need an interface and software for data collection. What do I need for data collection?

## Advanced Physics with Vernier — Beyond Mechanics

See other experiments from the lab book.

 1 Behavior of a Gas 2 Heat Engines 3 Standing Waves on a String 4 Standing Waves in a Column of Air 5 Doppler Effect 6 Electrostatics 7 Coulomb's Law 8 Mapping Electric Potential 9 Factors Affecting Electrical Resistance 10 Series and Parallel Circuits 11 Faraday’s Law: Moving Magnet 12 Faraday’s Law: Alternating Current 13 Capacitors and Inductors 14 RLC Circuits 15 Curved Mirrors and Images 16 Thin Lenses and Real Images 17 Thin Lenses and Virtual Images 18 Aperture and Depth of Field 19 Interference 20 Diffraction 21 Spectrum of Atomic Hydrogen 22 Planck’s Constant

### Experiment 19 from Advanced Physics with Vernier — Beyond Mechanics Lab Book

#### Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.