Mammoth Memory

Laterally inverted

We already know that the image in a mirror is

Behind the mirror (Virtual)
Equal distance
Same size
Upright

But perhaps we should add one more criteria:

Laterally inverted

 

You can remember what laterally means by thinking of a human. The lats on a human are on the sides of your back.

Lateral muscles on a persons back

Laterally – means sideways

 

This came about because if you hold a word up in front of a mirror it looks like the word has flipped sideways (not up and down).

See below for a view of the word ambulance reflected in a mirror.

Ambulance viewed in a mirror

But "sideways" is not quite correct.

If you stand infront of a mirror and lift your right hand it will look like you are lifting your left hand. It is interesting that both are pointed to the same side.

Looking in a mirror and pointing to the right with your right hand

But if you now point to yourself it will look like you are pointing in opposite directions.

Looking in a mirror and pointing at yourself

The way to think about lateral inversion is to remember what a hand impression in mud would look like.

Hand and imprint left in mud

The imprint of your left hand would look like the right hand. 

It's not east to west that have been reversed it's the front and back that has been reversed. The person has been pushed back and forwards like turning a glove inside out.

The actual inversion is of the `Z` axis (if we ever need to get technical).

X, Y and Z axis

To plot how a word is laterally inverted you apply the same laws of reflection that we have already learnt.

The first stage is to draw an image on the other side of the mirror perpendicular (at 90°) to the mirror.

Behind the mirror
Equal distance
Same size

In the example of reflecting the word "No" in a mirror we can work out what the image would look like in a mirror.

The word No in front of a mirror

This would become the following:

Marking the top and bottom of each letter is the first stage

NOTE: First plot the tops and bottoms of each of the letters.

Finally this would become:

The object word NO reflected in a mirror to produce an image word

The image word is how the word NO would look if you held it up infront of a mirror.

 

Conclusion

If you are asked in an exam to describe three properties of the image you see in a plane mirror you can say.

Behind the mirror (virtual)

Equal distance

Same size

Upright

and now – Laterally inverted

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