Reflection and Mirrors - Mission RM10 Detailed Help

A local drug store has installed a convex mirror with a focal length of -82.3 cm in an effort to monitor the aisles and reduce theft. Robin Storz stands a distance of 3.2 m from the mirror as he inspects the candy aisle. What is the corresponding image distance (in cm)? (Careful with units.)

The mirror equation relates the object distance (do), the image distance (di) and the focal length (f):
1 / do + 1 / di = 1 / f

The mirror equation, with its three reciprocal terms, is a little awkward to work with. It's recommended that you begin this problem by performing an algebra step to rearrange the equation such that the image distance (the unknown) is by itself on the left side of the equation. Then substitute the two numerical values into the equation and use your calculator to evaluate the right side. Once done, the reciprocal of the image distance is equal to the number on your calculator. Take the reciprocal of this number to determine the image distance.

When solving problems in physics, it is always important to give attention to the units used on given quantities. In this question, the unit given on the focal length and the object distance are different. To determine the image distance in meters, it will be necessary to convert the object distance in meters to units of centimeters. There are 100 of the smaller centimeters in 1 meter.

The Minds On Physics program calculates answers accurate to the fourth decimal place. Your answer does not need to be that accurate. The program will allow you to have a 1 percent deviation from the right answer without being wrong. This means two things: 1) Enter your answer with at least three significant digits. 2) Do not round any numbers until your final calculation.


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