Solving Plane Mirror Question: How Far is the Flagpole?

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SUMMARY

The discussion revolves around calculating the distance from a flagpole using a plane mirror. The mirror is 900 cm² in area and held 45 cm from the observer's eyes, who can see the full height of an 8.5 m flagpole. To solve the problem, participants emphasize converting the flagpole's height to centimeters and suggest using geometric principles, specifically similar triangles, to determine the distance from the pole. Consistency in units is crucial, with a recommendation to use the MKS (meter-kilogram-second) system for clarity.

PREREQUISITES
  • Understanding of geometric principles, specifically similar triangles.
  • Knowledge of unit conversion, particularly from meters to centimeters.
  • Familiarity with the properties of plane mirrors.
  • Basic skills in sketching and visualizing geometric problems.
NEXT STEPS
  • Learn how to apply similar triangles in optics problems.
  • Study the properties and calculations involving plane mirrors.
  • Explore unit conversion techniques in physics problems.
  • Practice solving mirror and lens questions with varying complexities.
USEFUL FOR

Students studying optics, physics educators, and anyone interested in solving geometric problems involving mirrors and distances.

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If you hold a 900cm squared plane mirror 45 cm from your eyes and can just see the full length of an 8.5 m flagpole behind you, how far are you from the pole.



I am doing mirror/lens questions and for some reason this one stumps me. I am assuming that the 8.5 m has to be changed to cm. However, i have been dealing with questions of radius of curvature and focal length and then this one seems really easy but it has stumped me? can anybody help please?
 
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dev-hud said:
If you hold a 900cm squared plane mirror 45 cm from your eyes and can just see the full length of an 8.5 m flagpole behind you, how far are you from the pole.



I am doing mirror/lens questions and for some reason this one stumps me. I am assuming that the 8.5 m has to be changed to cm. However, i have been dealing with questions of radius of curvature and focal length and then this one seems really easy but it has stumped me? can anybody help please?

Convert the area you are given for the mirror into its height. Then use a sketch to figure out the triangles to get to the answer. And yes, you need to be consistent with your units. I'd put everything in mks, myself.
 

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