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๐ฌ Think about it
Look in a mirror and wave your right hand. Your reflection waves its left! Why does a mirror swap left and right but not up and down? Let us explore the image in a plane mirror.
What kind of image does a plane mirror form?
- The image appears to be behind the mirror.
- It is the same size as the object.
- It is upright, which is called erect.
- It cannot be caught on a screen.
Example:
A pen held in front of a mirror has an image that looks like the same pen standing behind the mirror.
Object
Image in a plane mirror
In front of the mirror
Appears behind the mirror
Has a real size
Same size as the object
The real thing
Erect and cannot be caught on a screen
What is lateral inversion?
- Stand close to a mirror and the image is close too.
- Stand far away and the image looks far too.
- Your left appears as right in the image, and right as left.
- This left-right swap is called lateral inversion.
Example:
The word AMBULANCE is written reversed on the front of the vehicle so it reads correctly in a rear-view mirror.
In this Activity, we will study the size and nature of the image of a pen in a plane mirror.
Materials needed
A plane mirror, a pen or other object, and a screen.
Procedure
1. Place the pen in front of the mirror and look at its image.
2. Move the pen to different positions and compare the image sizes.
3. Check whether the image stays upright at each position.
4. Place a screen behind the mirror, then in front, and check for the image.
2. Move the pen to different positions and compare the image sizes.
3. Check whether the image stays upright at each position.
4. Place a screen behind the mirror, then in front, and check for the image.
Observation
The image is the same size as the pen, is erect, and cannot be caught on a screen.
Explanation
A plane mirror forms an image that is the same size, erect, and behind the mirror, so it cannot be obtained on a screen.
โ Summary
- Image same size as pen
- Image is erect
- Image is behind mirror
- Not caught on screen
In this Activity, we will check how the image distance changes with our distance from the mirror.
Materials needed
A plane mirror (large enough to see yourself).
Procedure
1. Stand in front of the mirror and notice how far the image appears.
2. Stand close to the mirror and check if the image is also close.
3. Stand at different distances and observe the image distance each time.
4. Look for a relation between your distance and the image distance.
2. Stand close to the mirror and check if the image is also close.
3. Stand at different distances and observe the image distance each time.
4. Look for a relation between your distance and the image distance.
Observation
When you stand close, the image is close; when you stand far, the image looks far.
Explanation
The image distance behind the mirror matches your distance in front of it. So the image moves as you move.
โ Summary
- Stood at different distances
- Close object, close image
- Far object, far image
- Distances match
๐ฉพ Fascinating Facts
- Long ago, mirrors were made by polishing stone or metal.
- When glass mirrors came, the art of metal mirrors faded.
- It still survives in Kerala as the Aranmula Kannadi.
- This is a unique metal-surface mirror made for centuries.
Important Points
- A plane mirror image is same size, erect, and behind the mirror.
- It cannot be caught on a screen.
- The image shows left-right reversal called lateral inversion.
โ Test Yourself
-
Is the image in a plane mirror the same size as the object?
View Answer
Yes, it is the same size. -
What does erect mean?
View Answer
Upright, the right way up. -
Can the image be caught on a screen?
View Answer
No, it cannot. -
What is lateral inversion?
View Answer
The left-right reversal of the image in a plane mirror. -
Why is AMBULANCE written reversed on the vehicle?
View Answer
So it reads correctly in a rear-view mirror.
Important Definitions
- Image — the likeness of an object that appears to be behind a plane mirror.
- Erect image — an image that is upright, the same way up as the object.
- Lateral inversion — the left-right reversal seen in an image formed by a plane mirror.
๐ NCERT Question 8 — Write your name on
Write your name on paper and hold it in front of a plane mirror. Sketch the image. What difference do you notice?
View Answer →
๐ NCERT Question 10 — On the basis of
On the basis of two statements about lateral inversion and the letters T and O, choose the correct option.
View Answer →
