Plane Mirror Imaging Simulator Guide

Overview

When looking in the mirror every morning, have you ever wondered: how far is the "you" in the mirror from the mirror surface? Does its size change as you approach? Plane mirror imaging is one of the most fundamental and interesting phenomena in geometric optics. This experiment simulates the imaging process of a candle in front of a plane mirror to help you observe and verify the perfect "symmetry aesthetics" between the image and the object.

Background

• As early as 2000 BC, ancient Egyptians and Chinese began using polished copper mirrors.
• Legend has it that Archimedes used a huge array of mirrors to reflect sunlight and burn Roman warships attacking Sicily. Although the authenticity is questionable, it reflects the ancients' profound understanding of the principle of light reflection.
• In 1835, German chemist Justus von Liebig invented the silvered glass mirror, which made high-reflectivity mirrors popular and benefited modern optical experiments.

Key Concepts

Formulas & Derivation

Experiment Steps

1. 1

   Observe Initial Imaging

   At the beginning of the experiment, a candle is placed in front of the mirror. Observe the image appearing behind the mirror. Is it upright or inverted? Is it a real image or a virtual image? (Hint: Virtual images are usually drawn with dashed lines)
2. 2

   Explore Distance Relationship

   Drag the candle left or right to change the object distance $u$. Observe how the image distance $v$ changes? Try stopping at any position and compare the values of $u$ and $v$.
3. 3

   Verify Equal Size Property

   Adjust the "Object Height" slider to change $h$. Observe if the height of the image in the mirror $h'$ changes accordingly? When you move away from the mirror, the image looks smaller, but is the image really getting smaller?
4. 4

   Trace Light Path

   Check "Show Virtual Rays". Observe how the light rays "enter" the eyes. The convergence point of the backward extensions of the reflected rays is the position of the image.

Learning Outcomes

• Confirm that the image formed by a plane mirror is an upright virtual image of equal size ($M=1$)
• Verify the quantitative relationship that image distance equals object distance ($v=u$)
• Clarify the geometric property that the line connecting the image and the object is perpendicular to the mirror surface
• Understand that the essence of plane mirror imaging is the reflection of light, following the law of reflection

Real-world Applications

• Periscope: Uses two plane mirrors to change the light path, allowing observation of the external environment from a concealed location.
• Vehicle Rearview Mirror: Although convex mirrors are often used to expand the field of view, the interior rearview mirror is usually a plane mirror used to judge the actual distance of vehicles behind.
• Dance Studio Mirror Wall: Uses plane mirror imaging to expand the visual space and facilitate dancers in correcting their posture.

Common Misconceptions

Further Reading

• Plane Mirror - Wikipedia