Mammoth Memory

Where can an observer see a reflected image?

If in an exam you were asked to find the area where an observer can see the image in a mirror, you would do so as follows:

Object and mirror

You need to apply the laws of reflection and initially draw an image on the other side of the mirror perpendicular (at 90°) to the mirror.

Behind the mirror
Equal distance
Same size

Image drawn the other side of the mirror

We end up with a diagram as follows:

Object image and mirror

The second stage is to draw rays from the object to the edges of the mirror and reflect off the edges, either

  1. So that the angle of incidence equals the angle of reflection
  2. Draw from the image to the points on the edges

Ray diagram showing the image of an object seen in a mirror

Between these two reflected lines any observer will be able to see a reflected image.

Ray diagram showing where an observer can see an object in a mirror


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