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š¬ Think about it
Your eyes can only see things above a certain size. For a long time, a whole world of tiny living things stayed hidden from us. Then one simple piece of curved glass changed everything. What was it, and how did it open up this hidden world? Let's find out.
What are organisms?
Organism
Living
it grows, feeds, and multiplies
Being
a plant or an animal, of any shape, size, or colour
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An organism is any living being — a plant or an animal — of any shape, size, or colour.
- All living beings are called organisms.
- They come in all shapes, sizes, and colours.
- Some are very big, while others are too tiny to see.
How were tiny things first made visible?
Who first opened the invisible world?
The microscope
Made tiny things visible
Robert Hooke
Looked at a slice of cork
Named them cells (1665)
Example:
Micrographia
Cork cells
Van Leeuwenhoek
Made much better lenses
Father of Microbiology
Example:
Bacteria
Blood cells
- People found a curved piece of glass makes small things look bigger.
- It was shaped like a lentil seed, so it was called a lens.
- Better lenses led to magnifying glasses and then the microscope.
What did the microscope reveal?
Before the microscope
After the microscope
Only things above a certain size could be seen.
Tiny things hidden from the eye became visible.
The tiny living world remained unknown.
A hidden world of tiny creatures was opened.
Nobody knew what living things were built from.
Cork was seen to be made of small empty spaces — cells.
- The microscope opened a hidden world of tiny living creatures.
- These are too small to see with our eyes alone.
- We will explore some of these life forms in this chapter.
How does a magnifying glass help us see small things?
How does a magnifying glass make things look bigger?
Curved glass
Thick in the middle, thin at the edge
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It bends the light
The rays coming from the object are bent
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The object looks larger than it really is
- A magnifying glass has a curved lens.
- The lens bends light to make small things look bigger.
- So we can see fine details our eyes alone would miss.
Example:
Looking at an ant through a magnifying glass, you can see the fine details of its body clearly.
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Activity 2.1 — Let us observe
How do we make the letters look bigger?
Fill a round-bottom flask with water
A glass flask, filled right up
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Close its mouth with a cork
So the water cannot spill
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Stand the flask on an open book
And look at the letters through it
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The letters look larger — the water-filled flask acts like a magnifying glass
In this Activity, we will observe how a water-filled flask makes letters look larger, and see what a lens really does.
Materials needed
A round-bottom glass flask, water, a cork, and an open book.
Procedure
1. Take a round-bottom glass flask and fill it with water.
2. Close the mouth of the flask with a cork.
3. Place the flask on an open book.
4. Look at the letters of the book through the flask.
2. Close the mouth of the flask with a cork.
3. Place the flask on an open book.
4. Look at the letters of the book through the flask.
Observation
The letters of the book look larger when seen through the water-filled flask.
Explanation
The water-filled flask acts like a magnifying glass. A curved lens bends light to make small things look bigger — the same idea used in a microscope.
A flask full of water bends light and acts like a magnifying glass, so the letters look larger.
ā Summary
- A water flask acts as a lens
- A lens makes small things bigger
- This idea led to the microscope
š Ever heard of ...
- In 1665, Robert Hooke published a book called Micrographia .
- His microscope made things look 200–300 times bigger.
- In a slice of cork he saw tiny boxes and named each a "cell".
- Around the same time, van Leeuwenhoek first saw bacteria.
- So he is called the Father of Microbiology.
