3. When examining microscopy images it is always important to keep in mind what

Question

3. When examining microscopy images it is always important to keep in mind what the image magnification is so that you can magnifcation is not wien on the image but instead a size bar is provided. The listed size under the size bar is the actual size of the bar and you can use a ruler to determine the image size of the bar. In this image of Streptococcus pneumonia the size bar would measure 9 mm on a ruler and the bacterial cell is 3 cm in diameter. Use this information to answer the following two questions. a. What is the magnification of this image? b. What is the actual diameter of S pneumonia? 200 nm kin c. Is this picture taken using a light microscope or an electrorn microscope? How do you know? d. What specific type of microscope (i.e. what classification of light or electron scope) do you think took this picture?

Explanation / Answer

Let us first have the answers to the questions befor having detailed explanation of the topic:

Answers:

a. Magnification of the given microscope = 45,000x

b. Actual diameter of S. Pneumonia is 666.67 nm

c. The picture is taken with ELECTRON MICROSCOPE

d. Type of electron microscope for taking the picture is Scanning Electron microscope (SEM)

Explanation:

a. Magnification of the image is the ratio of size of image to size of object which can be written as follows:

Magnification = Size of image / Actual size of object

The first question is about the magnification of the image,

Given that, Size of the image =9mm i.e 9000,000 nm (since 1mm= 1000,000nm), actual size of object (size bar on the image)= 200nm

Then, Magnification = Size of image / Actual size of object

= 9000,000/200

= 45,000x

Magnification of the given microscope = 45,000x

b. Actual size (diameter) of object (S. pneumonia) = Size of image/ Magnification

Given that size of image = 3cm i.e., 30000,000 nm (since 1cm=10000,000nm), and magnification we already found it as 45,000x

Then, Actual size (diameter) of object (S. pneumonia)= 30000,000/45,000

= 666.67 nm

Hence the actual diameter of S. Pneumonia is 666.67 nm

c. The picture is taken with ELECTRON MICROSCOPE

How can we know?

i. The typical resolution of light microscope is 200nm, with magnification between 1000x to 2000x whereas the electron microscope has a resolution of 0.5nm, with magnification upto 100,000x (Scanning electron microscope), 250,000x (Transmission electron microscope).

Since the magnification is 45,000x, light microscope cannot be utilised to produce such magnification, it can be achieved only using electron microscope

ii. Natural colour or stain colour is observed when light microscope is used, whereas true colours are not seen in electron microscope as they are collected on photographic plates or fluorescent screens. As the above image is in the grayscale, it is quite obvious fact that it is taken using Electron microscope.

d. Type of electron microscope for taking the picture is Scanning Electron microscope (SEM)

How to conclude? Scanning electron microscope gives a 3dimensional view of the sample, in the given picture, the surface morphology of S. pneumonia is clearly seen (shadows, elevations and depressions in the cell), hence it can be concluded that Scanning electron microscope is used.

Transmission electron microscope gives only 2dimensional flat images as the electron beam is transmitted through the sample, which is not the case with the given picture.

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.