Vernier Software & Technology

# Diffraction

## 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. Because Newton was unable to observe the diffraction of light, he concluded that it could not be wave-like. Thomas Young’s double-slit experiment in the early 19th century provided convincing evidence that supported the wave model of light. This is the second of two experiments in which you will examine the related phenomena of diffraction and interference.

## 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 Huygen’s Principle to construct a diagrammatic explanation of how path length differences for waves originating at different points in the slit give rise to the dark fringes in a diffraction pattern.
• From experimental parameters, predict the locations of 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 20 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.