Drawing images in a plane mirror involves understanding how light reflects and tracing light rays from an object to the mirror and then into the observer's eye.
To draw an image formed by a plane mirror, you typically use ray diagrams that show how light rays originating from the object reflect off the mirror and appear to come from a point behind the mirror, which is where the virtual image is located. As the reference mentions, when light hits a flat surface like a plane mirror, it reflects according to the laws of reflection. Specifically, a ray hitting the mirror perpendicularly bounces directly back.
Understanding Image Formation
A plane mirror forms a virtual image. This means the light rays do not actually converge at the image location behind the mirror; instead, they appear to diverge from that point. This is why you can see the image but cannot project it onto a screen.
Steps to Draw a Plane Mirror Ray Diagram
Drawing a ray diagram helps visualize how the image is formed. You need at least two light rays originating from a single point on the object to find the corresponding point on the image.
Here are the steps:
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Represent the Mirror, Object, and Principal Axis:
- Draw a straight line for the plane mirror, often with dashed lines on the back to indicate the reflective surface.
- Draw the object in front of the mirror. A simple arrow or point is often used.
- Draw a principal axis perpendicular to the mirror, though this is less critical for a simple plane mirror than for curved mirrors.
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Draw the First Light Ray:
- From a point on the object (e.g., the top of an arrow), draw a ray of light that hits the mirror perpendicularly (at a 90-degree angle).
- Based on the reference, this ray hits the flat surface (the mirror) and will "bounce. Directly back." Draw the reflected ray along the same path as the incident ray, but with an arrow indicating the direction of reflection.
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Draw the Second Light Ray:
- From the same point on the object, draw another ray of light that hits the mirror at an arbitrary angle.
- Apply the Law of Reflection: The angle of incidence (angle between the incoming ray and the mirror's normal line) equals the angle of reflection (angle between the reflected ray and the normal). Draw the reflected ray obeying this law.
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Locate the Image Point:
- Extend the reflected rays behind the mirror using dashed lines. These dashed lines represent the apparent path of the light from the perspective of an observer.
- The point where these extended dashed lines intersect behind the mirror is the location of the image point corresponding to the point you chose on the object.
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Repeat for Other Points (if necessary):
- If the object is more complex (like an arrow), repeat steps 2-4 for other key points (e.g., the tail of the arrow) to determine the full image.
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Draw the Image:
- Connect the image points behind the mirror to form the complete image.
Characteristics of the Image Formed by a Plane Mirror
The image formed by a plane mirror always has specific characteristics:
- Virtual: The image is formed by the apparent intersection of reflected rays, not actual rays.
- Upright: The image is oriented the same way as the object (not inverted).
- Same Size: The image is the same size as the object.
- Same Distance: The image appears as far behind the mirror as the object is in front of it.
- Laterally Inverted: The image is reversed left-to-right (e.g., text appears backward).
Summary Table
| Characteristic | Description |
|---|---|
| Type | Virtual |
| Orientation | Upright |
| Size | Same size as the object |
| Distance | Same distance behind the mirror as object is front |
| Inversion | Laterally inverted (left-right reversed) |
By following these steps and understanding the principles of light reflection, you can accurately draw the image formed by an object in a plane mirror.
