## Lesson 4: Interference of Light Waves

## Overview:

In this activity, you will analyze the interference of light waves, both qualitatively and quantitatively. You will learn about Thomas Young's famous double-slit experiment, and you will have the opportunity to investigate Young's double slit experiment with the help of animated simulations. You will explore the derivations of the equations relevant to analyzing two-dimensional wave interference and practice applying these equations.

## Curriculum Expectations:

**Overall Expectations:**

**E2.**Investigate, in qualitative and quantitative terms, the properties of waves and light, and solve related problems.

**E3.**Demonstrate an understanding of the properties of waves and light in relation to diffraction, refraction, interference, and polarization.

**Specific Expectations:**

**E2.1**Use appropriate terminology related to the wave nature of light, including, but not limited to: diffraction, dispersion, wave interference, nodal line, phase, oscillate, polarization, and electromagnetic radiation.

**E2.3**Conduct inquiries involving the diffraction, refraction, polarization, and interference of light waves (e.g., shine lasers through single, double, and multiple slits; observe a computer simulation of Young’s double-slit experiment; measure the index of refraction of different materials; observe the effect of crossed polarizing filters on transmitted light).

**E2.4**Analyze diffraction and interference of water waves and light waves (e.g., with reference to two-point source interference in a ripple tank, thin-film interference, multiple-slit interference), and solve related problems.

## Success Criteria:

- Why is it necessary to have a monochromatic light source in the double slit experiment?
- What is the path length difference given by in Young's double slit experiment?
- What is the condition required for constructive interference and a bright interference fringe to occur?
- What is the condition required for destructive interference and a dark fringe in the interference pattern to occur?
- The fringe at the centre of the screen has what value of m?
- How do you calculate the separation between any two adjacent fringes?

## Time Allocation: 4 hours

## Learning A

ctivities:**Read**pages 477 - 483 from Nelson 9.5

In the playlist below, video:

- Will show you how to calculate the fringes of the Young's double slit interference pattern.

**Practice**questions 1, 2, and 3 on page 482.

## Task:

**Complete**the assignment on Moodle: "Wave Interference Simulation."

**Solve**questions 2, 4, and 5 from Nelson 9.5 Review on page 484.

Quiz Chapter 9 on Moodle.

*Optional Extension:*- Solve questions 1 and 8 on page 484.

## Reflect:

Reflect on the concepts and facts that you learned in this chapter. Select one fact or concept that you found particularly interesting, to the point that you continued investigating the fact or concept in your daily life. Give some examples.