# Waves, Sound and Light: Light Waves

## Light Waves: Audio Guided Solution

#### Problem 15:

Mr. H’s period 7 physics class is attempting to duplicate Thomas Young’s experiment in which they use a two-point source light interference pattern to measure the wavelength of light. They red shine laser light through a slide containing a double slit; the slit spacing is 0.125 mm. The light interference pattern created by the light which passes through the slits is projected on a screen a distance of 10.72 m away. Justin and Shirley measure the distance from the 3rd antinodal bright spots on opposite sides of the pattern to be 33.9 cm apart. Based on these measurements, what is the wavelength of the red laser light.

## Habits of an Effective Problem Solver

• Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
• Identify the known and unknown quantities and record in an organized manner, often times they can be recorded on the diagram itself. Equate given values to the symbols used to represent the corresponding quantity (e.g., v = 3.00x108 m/s, λ = 554 nm, f = ???).
• Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
• Identify the appropriate formula(s) to use.
• Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.