Reflection and Mirrors Legacy Problem #5 Guided Solution
Problem*
Baldwin Young stands 68 cm from his dresser mirror, inspecting his scalp. How far is the image of his scalp located from his scalp?
Audio Guided Solution
One of the properties of plain mirror images that you can always count on is the property that the distance from the image to the mirror is equal to the distance from the object to the mirror. And here in this question, the object is a young man�s scalp, and it�s 68 centimeters from a mirror. Therefore, the distance that the image is from the mirror is also 68 centimeters. However, that�s not the answer, because the question is not, �What�s the image distance,� but, �What�s the distance from the image to the object?� And so if the distance from the object to the mirror is 68 centimeters, and the distance from the mirror to the image is 68 centimeters, all you have to do to get the answer is to add these two numbers, and they add up to 136 centimeters.
Solution
136 cm
Habbits 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 in an organized manner. Equate given values to the symbols used to represent the corresponding quantity - e.g., \(\descriptive{d_o}{d_o,distance object} = 24.2\unit{cm}\); \(\descriptive{d_i}{d_i,distance image} = 16.8\unit{cm}\); \(\descriptive{f}{f,focal length} = \colorbox{gray}{Unknown}\).
- 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.
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