Mirrors create virtual images when light rays from the same location on an object reflect off the mirror and diverge or spread apart.
When you look into a flat (plane) mirror, you see a reflection that appears to be behind the mirror. This is a classic example of a virtual image. Unlike real images, which can be projected onto a screen because the light rays actually meet, virtual images cannot be projected.
The Formation Process: Diverging Light Rays
Based on how light behaves, virtual images are formed through a specific interaction between light and the mirror surface.
As highlighted by the reference:
- Virtual images form when light rays from the same location on an object reflect off a mirror and diverge or spread apart.
- Real images form when light rays from the same location on an object reflect off a mirror and converge or come together.
For a virtual image to appear, light rays originating from a single point on an object strike the mirror and bounce off. Instead of coming together after reflection, these rays spread out. Our brain, accustomed to light traveling in straight lines, perceives these diverging rays as if they originated from a point behind the mirror where they would have met if they had traveled backward in a straight line. This apparent origin point is where the virtual image is located.
Virtual vs. Real Images: A Key Difference
Understanding the difference between how light rays behave after reflection is crucial to distinguishing virtual from real images.
| Image Type | Light Ray Behavior After Reflection | Projection |
|---|---|---|
| Virtual | Diverge (spread apart) | Cannot be projected |
| Real | Converge (come together) | Can be projected |
This fundamental difference in ray behavior after reflection determines the nature of the image formed.
Examples and Practical Insights
Virtual images are commonly encountered in everyday life:
- Plane Mirrors: The image you see in a bathroom mirror is always virtual, upright, and appears to be behind the mirror.
- Convex Mirrors: These curved mirrors (like those used as side-view mirrors on cars or in store aisles for security) always produce virtual, upright, and reduced images.
Here are some practical points about virtual images from mirrors:
- They always appear upright (the same orientation as the object).
- They cannot be captured on a screen because the light rays do not physically meet at the image location.
- The size and distance of a virtual image depend on the type of mirror (plane, convex) and the object's position.
- In the case of a plane mirror, the virtual image is the same size as the object and appears as far behind the mirror as the object is in front.
Understanding how mirrors cause light rays to diverge explains the formation of the non-projectable, apparent images we call virtual images.
