Curriculum
Science Grade IX
Microscopy
School Revise · Grade 9 · Advanced Science (Optional) · Chapter 9
Microscope and Microscopy
Science at Advanced Level, Class 9. This optional chapter explains how microscopes reveal the tiny world, the difference between magnification and resolution, the parts of a compound microscope, and electron microscopes.
|
|
||
|
|
What this chapter is about
A microscope opens a world too small for the eye. In this chapter we separate two ideas that are often confused, magnification and resolution, name the parts of the compound microscope you use in school, and see how electron microscopes see far finer detail.
1. Magnification and resolution
|
Magnification and resolution magnification is how many times larger the image is; resolution is the smallest gap you can still see as two points More magnification is not always better. If the resolution is poor, a bigger image is just a bigger blur. The human eye resolves about 0.1 mm, a light microscope about 0.2 µm, and an electron microscope about 0.2 nm. In real life: A phone can zoom into a photo, magnifying it, but past a point you only see bigger fuzzy squares, that is the limit of its resolution. |
|
Total magnification the total magnification is the objective magnification times the eyepiece magnification: M = m(objective) × m(eyepiece) The objective lens near the slide makes a first enlarged image, and the eyepiece enlarges that again. Multiplying the two gives the total. The real size of an object is the image size divided by M. In real life: A 10 times eyepiece with a 40 times objective magnifies 400 times, enough to see cheek cells clearly. |
|
Worked example 1 Question. A microscope has a 10× eyepiece and a 40× objective. Find the total magnification.
Answer: The total magnification is 400×. |
|
Worked example 2 Question. At 100×, a cell appears 5 mm across. Find its real size.
Answer: The cell is about 0.05 mm (50 µm) across. |
2. The compound microscope and electron microscopes
|
Light and electron microscopes a light microscope uses glass lenses and visible light; an electron microscope uses magnetic lenses and a beam of electrons Because electrons have a far shorter wavelength than light, electron microscopes resolve far finer detail. A TEM passes electrons through a thin slice for a 2D inside view; a SEM scans the surface for a 3D like image. In real life: The detailed pictures of a virus or a pollen grain in textbooks are taken with electron microscopes, far beyond a light microscope’s reach. |
|
Worked example 3 Question. At 40× the field of view is 4 mm. Predict it at 400× (field is inversely proportional to magnification).
Answer: The field of view is about 0.4 mm. |
Practise with the interactive
Try this chapter hands on: change the values and watch the result update live and animate. The interactive opens right here in the lesson.
Practice set A, multiple choice
1. Resolution is the …
Smallest distance between two points that can still be seen as separate; higher resolution shows finer detail.
2. Total magnification of a compound microscope is …
The objective magnification times the eyepiece magnification, M = m(objective) × m(eyepiece).
3. A SEM is best for viewing …
The three dimensional surface of a specimen, such as a pollen grain or an insect’s leg.
4. A 15× eyepiece and a 10× objective give a total magnification of …
| 1 | Multiply the two. 15 × 10. |
| 2 | Work it out. = 150×. |
Practice set B, short answer
1. Why is more magnification not always better?
Because if the resolution is poor, a larger image is simply a larger blur; you can only see extra detail if the resolution is good enough to separate the points.
2. A cell is 4 mm across at 200×. Find its real size.
| 1 | Real size = image / M. 4 mm / 200. |
| 2 | Work it out. = 0.02 mm, or 20 µm. |
3. Why can an electron microscope see finer detail than a light one?
Because electrons have a much shorter wavelength than visible light, and a shorter wavelength gives a much higher resolution, revealing far finer detail.
Quick summary
| Idea | The idea |
| Magnification | How many times larger the image is. |
| Resolution | Smallest gap seen as two points. |
| Total M | objective × eyepiece. |
| Real size | image size / M. |
| TEM | 2D inside view, thin slice. |
| SEM | 3D like view of the surface. |
| Open the Virtual Lab |
These free Grade 9 Advanced Science notes explain microscopes, magnification, resolution, the compound microscope and electron microscopy types, with clear step by step worked examples and labelled diagrams for every student using the optional Advanced Level book.
© 2026 School Revise. All rights reserved. This lesson is original content written by School Revise, aligned to the CBSE Class 9 Science at Advanced Level (Optional) syllabus. Unauthorised copying, reproduction or redistribution is not permitted. Curriculum names are used only to indicate alignment.
Google