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๐ฌ Think about it
You don't need a science centre — a shiny steel spoon is two curved mirrors in one. The inner dip flips your face upside down; the outer bulge shrinks it. That curved shape is the secret. Let's see what spherical mirrors are.
What do we see in the two sides of a shiny spoon?
- A shiny spoon acts like a mirror.
- The inner curved side shows an inverted image.
- The outer bulging side shows an erect, smaller image.
- So a curved surface changes the image.
Example:
Look into the bowl of a spoon and your face is upside down; flip it and your face shrinks.
In this Activity, we will use a shiny spoon to see how its two curved sides form different images.
Materials needed
A shiny metallic spoon.
Procedure
1. Hold the curved (inner) surface of the spoon close to your face.
2. Notice the image and compare it with a plane-mirror image.
3. Slowly move the spoon away and watch for any change.
4. Now flip the spoon and repeat the same steps with the outer side.
2. Notice the image and compare it with a plane-mirror image.
3. Slowly move the spoon away and watch for any change.
4. Now flip the spoon and repeat the same steps with the outer side.
Observation
The inner side shows an inverted image; the outer side shows an erect but smaller image.
Explanation
The spoon's surfaces are curved, so they act like spherical mirrors. The inward curve and outward bulge form different images, unlike a flat plane mirror.
โ Summary
- Spoon held to face
- Inner side inverts
- Outer side shrinks
- Curve matters
What are concave and convex mirrors?
- Spherical mirrors are shaped like part of a hollow sphere.
- A concave mirror curves inwards.
- A convex mirror curves outwards.
- The non-reflecting surface is shown shaded in diagrams.
Concave mirror
Convex mirror
Reflecting surface curves inwards.
Reflecting surface curves outwards.
Like the inner side of a spoon.
Like the outer side of a spoon.
In this Activity, we will tell concave and convex mirrors apart by looking at their curve from the side.
Materials needed
A concave mirror and a convex mirror.
Procedure
1. Place both mirrors on a table with reflecting surfaces facing up.
2. View them from the side with your eye at their level.
3. Identify whether each surface curves inwards or outwards.
2. View them from the side with your eye at their level.
3. Identify whether each surface curves inwards or outwards.
Observation
One surface dips inwards (concave) and the other bulges outwards (convex).
Explanation
Looking from the side shows the curve clearly, so you can tell a concave mirror from a convex one.
โ Summary
- Mirrors face up
- Viewed from side
- Curve identified
- Concave vs convex
๐ก A step further
- A spherical mirror is shaped like part of an imaginary hollow sphere.
- It is not cut from a glass sphere.
- It is made by grinding and polishing flat glass into a curve.
- A reflective coating on one curved side makes it concave or convex.
Important Points
- Spherical mirrors are shaped like part of a hollow sphere.
- Concave mirrors curve inwards; convex mirrors curve outwards.
- A side view shows whether a mirror is concave or convex.
โ Test Yourself
-
What is a spherical mirror?
View Answer
A mirror whose reflecting surface is shaped like part of a sphere. -
Which way does a concave mirror curve?
View Answer
Inwards, like the inner bowl of a spoon. -
Which way does a convex mirror curve?
View Answer
Outwards, like the back of a spoon. -
Which side of a spoon gives an inverted image?
View Answer
The inner curved side, which acts like a concave mirror. -
How is a spherical mirror made?
View Answer
By grinding and polishing flat glass into a curve, then adding a reflective coating to one curved side.
Important Definitions
- Spherical mirror — a mirror whose reflecting surface is part of a sphere.
- Concave mirror — a spherical mirror with a reflecting surface that curves inwards.
- Convex mirror — a spherical mirror with a reflecting surface that curves outwards.
๐ NCERT Question 9 — Match the entries in
Match concave/convex mirrors and convex/concave lenses with their correct descriptions.
View Answer →
