Microscopy Principle And Application

1.

What is the minimum distance for the eye to focus any object?

A.

A) 11 cm
B.

B) 25 cm
C.

C) 32 cm
D.

D) 4 2 cm

Correct Answer
B. B) 25 cm

Explanation
The minimum distance for the eye to focus any object is 25 cm. This is known as the near point or the closest point at which the eye can focus without straining. Beyond this distance, the eye's lens needs to adjust in order to focus on objects that are farther away.

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2.

Resolving power of a microscope is a function of____________

A.

A) Wavelength of light used
B.

B) Numerical aperture of lens system
C.

C) Refractive index
D.

D) Wavelength of light used and numerical aperture of lens system

Correct Answer
D. D) Wavelength of light used and numerical aperture of lens system

Explanation
The resolving power of a microscope is determined by both the wavelength of light used and the numerical aperture of the lens system. The wavelength of light affects the ability of the microscope to distinguish between two closely spaced objects, with shorter wavelengths allowing for higher resolution. The numerical aperture of the lens system determines the amount of light that can enter the microscope and also affects the resolution. Therefore, both factors contribute to the resolving power of a microscope.

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3.

Oil immersion objective lens has an NA value of____________

A.

A) 0.65
B.

B) 0.85
C.

C) 1.33
D.

D) 1.00

Correct Answer
A. A) 0.65

Explanation
The oil immersion objective lens has an NA (Numerical Aperture) value of 0.65. The NA value represents the ability of the lens to gather and resolve light. A higher NA value indicates a greater ability to gather and resolve light, while a lower NA value indicates a lower ability. In the case of the oil immersion objective lens, an NA value of 0.65 suggests that it has a moderate ability to gather and resolve light.

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4.

In Phase contrast microscopy, the rate at which light enters through objects is__________

A.

A) Constant
B.

B) Inversely proportional to their refractive indices
C.

C) Directly proportional to their refractive indices
D.

D) Exponentially related to their refractive indices

Correct Answer
B. B) Inversely proportional to their refractive indices

Explanation
In phase contrast microscopy, the rate at which light enters through objects is inversely proportional to their refractive indices. This means that objects with higher refractive indices will allow less light to pass through them, while objects with lower refractive indices will allow more light to pass through them. This is because the phase contrast technique enhances the visibility of transparent and unstained specimens by exploiting the differences in refractive index between the specimen and the surrounding medium.

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5.

Which of the following is used in electron microscope?

A.

A) electron beams
B.

B) magnetic fields
C.

C) light waves
D.

D) electron beams and magnetic fields

Correct Answer
D. D) electron beams and magnetic fields

Explanation
Electron microscopes use electron beams and magnetic fields to magnify and visualize specimens. Electron beams are used to illuminate the sample, and the interaction between the electrons and the sample produces signals that are then detected and used to create an image. Magnetic fields are used to control the path of the electron beam and focus it onto the sample. This combination of electron beams and magnetic fields allows for much higher resolution and magnification compared to light microscopes, which use light waves.

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6.

Electron Microscope can give a magnification up to ___________

A.

A) 400,000X
B.

B) 100,000X
C.

C) 15000X
D.

D) 100X

Correct Answer
A. A) 400,000X

Explanation
Electron microscopes use a beam of electrons instead of light to magnify objects, allowing for much higher magnification than traditional light microscopes. The correct answer, a) 400,000X, suggests that an electron microscope can achieve a maximum magnification of 400,000 times. This high level of magnification enables scientists to study extremely small structures and details at the nanoscale level.

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7.

Which of the following are true for electron microscopy?

A.

A) specimen should be thin and dry
B.

B) image is obtained on a phosphorescent screen
C.

C) electron beam must pass through evacuated chamber
D.

D) specimen should be thin and dry, image is obtained on a phosphorescent screen and electron beam must pass through evacuated chambe

Correct Answer
D. D) specimen should be thin and dry, image is obtained on a pHospHorescent screen and electron beam must pass through evacuated chambe

Explanation
Electron microscopy requires the specimen to be thin and dry in order for the electrons to pass through it easily. The image is obtained on a phosphorescent screen because the electrons that pass through the specimen interact with the screen, producing a visible image. Additionally, the electron beam must pass through an evacuated chamber to prevent the electrons from scattering or interacting with air molecules, which could distort the image. Therefore, all three statements are true for electron microscopy.

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8.

Negative Staining is used for examining _____________

A.

A) virus particles
B.

B) protein molecules
C.

C) bacterial flagella
D.

D) virus particles, protein molecules and bacterial flagella

Correct Answer
D. D) virus particles, protein molecules and bacterial flagella

Explanation
Negative staining is a technique used in microscopy to examine structures that are difficult to visualize using other staining methods. In negative staining, the background is stained, while the structure of interest remains unstained. This technique is particularly useful for visualizing virus particles, protein molecules, and bacterial flagella, as it allows for better contrast and resolution of these structures against the stained background. Therefore, the correct answer is d) virus particles, protein molecules, and bacterial flagella.

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9.

Where do we obtain the magnified image of the specimen in SEM?

A.

A) cathode ray tube
B.

B) phosphorescent screen
C.

C) anode
D.

D) scanning generator

Correct Answer
A. A) cathode ray tube

Explanation
In a scanning electron microscope (SEM), the magnified image of the specimen is obtained on a cathode ray tube (CRT). The CRT is a display device that uses a beam of electrons to create an image on a fluorescent screen. In an SEM, the electron beam scans the specimen surface, and the interactions between the beam and the specimen produce signals that are then used to form an image on the CRT. This allows for the visualization and analysis of the specimen at high magnification and resolution.

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10.

Which of the following techniques are used in Transmission Electron Microscopy (TEM) for examining cellular structure?

A.

A) Negative-Staining
B.

B) Shadow Casting
C.

C) Ultrathin Sectioning
D.

D) Negative-Staining, Shadow Casting, Ultrathin Sectioning, Freeze-Etching

Correct Answer
D. D) Negative-Staining, Shadow Casting, Ultrathin Sectioning, Freeze-Etching

Explanation
Transmission Electron Microscopy (TEM) is a powerful technique used to examine cellular structures. Negative-Staining involves adding a contrasting agent to the sample, which creates a dark background and enhances the visibility of the cellular structures. Shadow Casting involves coating the sample with a thin layer of metal, creating a shadow effect that helps visualize the surface features. Ultrathin Sectioning involves cutting the sample into extremely thin slices, allowing for detailed examination of the internal structures. Freeze-Etching involves freezing the sample and then removing the ice to reveal the surface structures. Therefore, all of these techniques are used in TEM for examining cellular structure.

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