Ray Optics: Refraction and Lenses

Refraction and Lenses: Audio Guided Solution

Problem 21:

During an in-class exploration lab, students are looking through both converging and diverging lenses at various objects and observing the characteristics of the images. Moses becomes particularly intrigued by the diverging lens. He places it a distance of 4.8 cm from the lettering of his textbook and estimates that the image of the letters are one-fourth the size of the actual lettering.
a. Calculate the image distance which results when Moses holds the lens this close to the textbook.
b. Calculate the focal length of the lens.

Audio Guided Solution

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 them in an organized manner. Equate given values to the symbols used to represent the corresponding quantity - e.g., d_o = 24,8 cm; d_i = 16.7 cm; 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.

Read About It!

Get more information on the topic of Refraction and Lenses at The Physics Classroom Tutorial.

• Object-Image Relationships for Converging Lenses
• Object-Image Relationships for Diverging Lenses
• The Mathematics of Lenses

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