Lesson 1.4 - Calculating  

When you look into a microscope, you see very small objects, but how small are they?  You are going to learn how much larger a microscope makes a specimen appear.

The magnification power tells us how much larger the specimen appears.  For example, a lens with a power of 10X makes the specimen look ten times larger than it really is. 

Two sets of lenses are used to view the specimen.  One is located in the eyepiece, and the other is one of the objective lenses.  Refer to page 160: find the eyepiece (G) and the objective lens (E).  To determine the total magnification of your object, you must include both lens.

Do this by multiplying the power of the eyepiece and the power of the objective lens being used. {Magnification is an increase in size of an object.} 


Example :

In a compound microscope, the power of the eyepiece is 10X and the objective lens that you have lined up is 4X.  What is the total magnification of the object you are looking at?  How much bigger are you seeing it?

Total magnification =  eyepiece X objective lens
                                 =  10    X    4 
                                 =  40X
The total magnification of the object viewed in this example is 40X.

Study How to Calculate the Magnification of Samples on page 163 of the textbook; then, answer the questions below the interesting facts.

Question 1. Calculate the total magnification if a microscope has an eyepiece with a magnification of 10X and an objective lens with a magnification of 30X. 

Question 2. Which one of these is the most appropriate to magnify small objects up to 10X? 
- compound microscope    
- electron microscope
- hand lens
- dissecting scope

Question 3. Which ONE of these is the most appropriate to magnify small objects up to 20X? 
- compound microscope    
- electron microscope
- hand lens
- dissecting scope

Question 4. Which one of these is the most appropriate to magnify small objects up to 1000X? 
- compound microscope        
- electron microscope
- hand lens
- dissecting scope

Question 5. Which one of these is the most appropriate to magnify small objects many thousands of times? 
- compound microscope    
- electron microscope
- hand lens
- dissecting scope

Question 6. Answer the Check Your Understanding question 2 on page 164.

Question 7. Answer the Check Your Understanding question 3 on page 164.

 

Then, return here to continue this lesson.

 

 

               Enrichment and Interesting Facts
The magnification power is labelled on the side of the lens. 

The power is written as a number on the eyepiece and on each objective lens as the arrows show.

 

Now, do Assignment 8A.  Page forward to access the computer-scored assignment.   

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. Calculate the total magnification if a microscope has an eyepiece with a magnification of 10X and an objective lens with a magnification of 30X. 

Multiply the two lens powers: 10 x 30 = 300
This microscope is magnifying the object 300X larger. 

Question 2. Which one of these is the most appropriate to magnify small objects up to 10X? 

Scientists would use a hand lens to magnify an object 10X.

Question 3. Which ONE of these is the most appropriate to magnify small objects up to 20X? 

Scientists would use a dissecting scope to magnify an object 20X.

Question 4. Which one of these is the most appropriate to magnify small objects up to 1000X? 

Scientists would use a compound microscope to magnify an object 1000X.

Question 5. Which one of these is the most appropriate to magnify small objects up to many thousands of times? 

Scientists would use an electron microscope to magnify an object thousands of times..

Question 6. Answer the Check Your Understanding question 2 on page 164.

Under low power you can locate the specimen more easily.

Question 7. Answer the Check Your Understanding question 3 on page 164.

With the medium and high power objective lenses the coarse adjustment knob will take the object out of focus too quickly and there is the risk of hitting the slide with the lens; you could damage the lens and the slide.

 

  Click to return to where you left off in this lesson.

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