Biology: Observing Bacteria with Microscopes

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What is the primary reason for using oil immersion technique in light microscopy?

To reduce the refractive index of the objective lens

To change the color of the specimen

To increase the size of the specimen

To increase the resolution of the microscope (correct)

What is the purpose of immersing the objective lens and the specimen in a transparent oil of high refractive index?

To make the bacteria more visible

To increase the wavelength of visible light

To increase the numerical aperture of the objective lens (correct)

To decrease the size of the bacteria

Why should you not use the coarse focus knob when using the 100X objective?

Because it will decrease the size of the bacteria

Because it will break the slide (correct)

Because it will change the color of the specimen

Because it will increase the resolution of the microscope

What should you do before rotating the x100 objective into position?

Put a drop of oil immersion fluid on the slide Signup and view all the answers

What is the typical dimension range of bacteria?

0.5μm to 5μm Signup and view all the answers

What is the purpose of using the fine focus knob when using the 100X objective?

To refocus the microscope Signup and view all the answers

What is the purpose of heating the slide over the flame of the burner during the Gram staining process?

To kill the bacteria cells Signup and view all the answers

Why is it essential to use a thin smear of bacteria during the Gram staining process?

To allow the stain to penetrate the cells more easily Signup and view all the answers

What is the purpose of using immersion oil during the Gram staining process?

To increase the resolution of the microscope Signup and view all the answers

Why is it important to use known cultures side by side with the test organism during the Gram staining process?

To determine the Gram reaction of the test organism Signup and view all the answers

What is the purpose of using crystal violet in the Gram staining process?

To stain the bacteria cells Signup and view all the answers

What is the purpose of washing the slide with water after adding crystal violet during the Gram staining process?

To remove excess crystal violet Signup and view all the answers

What is the purpose of observing the slide under oil immersion?

To increase the magnification of the microscope Signup and view all the answers

What is the result of Gram-positive bacteria after staining and washing with alcohol?

They retain the crystal violet stain Signup and view all the answers

What is the purpose of using 95% alcohol in the Gram staining process?

To decolorize the bacteria Signup and view all the answers

What is the function of safranin in the Gram staining process?

To act as a counter stain Signup and view all the answers

What is the result of Gram-negative bacteria after staining and washing with alcohol?

They lose the violet stain and retain the red coloration Signup and view all the answers

What is the importance of iodine in the Gram staining process?

To bind the crystal violet stain to the bacteria Signup and view all the answers