# Waves, Sound and Light: Light Waves

## Light Waves: Audio Guided Solution

#### Problem 20:

The Bluebird Library has been celebrating the lives of famous scientists. Each month, a new scientist is selected and displays are created to feature the discoveries and contribution of the scientist. April's scientist of the month is Thomas Young; the library wishes to develop a Young's experient display. The library has purchased a blue laser which emits light with a wavelength of 473 nm. They also have purchased a slide with a double slit; the slit spacing is 44 µm. The library's current plans are to project the interference pattern onto a white board which is 3 feet wide and located 28 feet from the slits. What is the maximum number of bright spots which will appear on the board at these distances and what is the spacing distance between each bright spot? Assume that each bright spot is bright enough to see. (GIVEN: 1 m = 3.28 ft, 1 m = 106 mm, 1 m = 109 nm)

## Audio Guided Solution

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## 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.