Microscopy and Gram Staining C2

1. Which organism did Robert Koch first prove to cause anthrax?

• Mycobacterium tuberculosis

• Bacillus anthracis

• Escherichia coli

• Staphylococcus aureus

1. What is the main function of a convex lens in microscopy?

• To scatter light

• To focus light at a specific point

• 1. To increase magnification

• 1. To reduce image size

1. In microscopy, what is used to reduce light refraction at high magnifications?

• Immersion oil

• High-intensity light

• High-intensity light

• Lower magnification lenses

1. Which of the following best describes the principle of fluorescence microscopy?

• Light rays are refracted through a lens

• UV light excites electrons to emit fluorescence

• Light passes through a stained specimen

• Magnification is achieved using immersion oil

1. Why should focusing always begin with the lowest objective lens in Brightfield microscopy?

• To ensure proper alignment for higher magnifications

• To avoid damaging the sample

• To prevent refractive issues

• To enhance image contrast

1. What happens to light as it passes from air to glass in microscopy?

• 1. Its wavelength decreases

• It refracts due to a change in velocity

• Its frequency increases

• Its amplitude decreases

If a high-magnification image is blurry, which should you adjust first

• Increase light intensity

•  Use the fine adjustment knob

• Use the coarse adjustment knob

• 16. Switch to a higher objective

Which of the following best explains the purpose of Gram staining?

• To identify the shape of the bacteria

• To differentiate bacteria based on their ability to produce toxins

• To distinguish between bacteria with different cell wall structures

• To determine the motility of bacterial cells

Why is crystal violet used in the Gram staining procedure?

• It helps in retaining the color in Gram-positive bacteria.

• It is a counterstain to differentiate bacteria.

• It dissolves the outer membrane of Gram-negative bacteria.

• It decolorizes the bacteria to enhance visualization.

Which stain is used as the counterstain in Gram staining to differentiate between Gram-negative and Gram-positive bacteria?

• Safranin

• Methylene blue

• Crystal violet

• Carbol fuchsin