Lab 4: Microscopes and Prokaryotes

Questions and Answers

What is the minimum distance at which two points can be distinguished as separate by the human eye?

50 µm

500 µm

100 µm (correct)

10 µm

What is the role of the objective lens in a compound microscope?

It projects the final image to the eye.

It focuses the parallel rays of light.

It adjusts the focal length.

It magnifies and projects the image into the body tube. (correct)

Resolution allows the eye to distinguish between two objects. What enhances this ability?

Using higher brightness in the light source.

Increasing magnification. (correct)

Decreasing the distance between the objects.

Using a larger lens size.

When a convex lens focuses light rays, what point is formed?

The focal point Signup and view all the answers

What is the total magnification achieved by a microscope?

Product of the objective lens magnification and ocular lens magnification. Signup and view all the answers

What happens to the resolving ability of the eye when an object is brought closer using a lens?

It improves. Signup and view all the answers

Which of the following is a characteristic of a compound microscope?

It utilizes two or more lenses working in tandem. Signup and view all the answers

What is focal length in the context of a lens?

The distance between the center of the lens and the focal point. Signup and view all the answers

What is the correct action to take before increasing magnification on a microscope?

Ensure the specimen is in the center of the field of view. Signup and view all the answers

When using a microscope, what should you avoid doing when adjusting focus after moving to medium or high power?

Utilize the coarse focus to ensure clarity. Signup and view all the answers

How should light intensity be regulated when using a microscope?

By using the iris diaphragm and adjusting the condenser. Signup and view all the answers

What is the purpose of using a ruler when estimating the size of an object on a microscope?

To obtain the actual size by comparing with a known length. Signup and view all the answers

Which component of the microscope is used to improve image clarity after focusing?

The fine focus knob. Signup and view all the answers

What should be done with the microscope after use?

Ensure the lenses are clean and cover it before storing. Signup and view all the answers

What is the first step in estimating the size of an object using a ruler?

Center the object in the field of view. Signup and view all the answers

What is a consequence of forgetting to return to low power before removing the slide?

The coarse focus knob could scratch the slide. Signup and view all the answers

What happens to the working distance as magnification increases?

The working distance decreases. Signup and view all the answers

What should you avoid using for cleaning the microscope lenses?

Paper towels Signup and view all the answers

Which focusing knob should only be used at low power?

Coarse focus knob Signup and view all the answers

How should microscopes be carried to prevent damage?

Carried upright with two hands. Signup and view all the answers

What is the effect of increasing magnification on the focal plane?

The focal plane decreases. Signup and view all the answers

What precaution should be taken regarding electric cords around microscopes?

Position cords to avoid tripping hazards. Signup and view all the answers

What should be done before turning on the illuminator on a microscope?

Make sure the stage is lowered and the lowest power objective lens is in place. Signup and view all the answers

What is the recommended action when focusing on a specimen?

Keep focusing up and down with the fine focus knob. Signup and view all the answers

Study Notes

Microscopy Review

Human eye resolution is limited to objects at least 100 µm apart; closer objects appear as a single entity.
Resolution is the ability to distinguish between two close points; increasing magnification enhances this capability.
Objects appear larger when viewed through lenses; this improves resolving power by spreading the image over more receptor cells.
Compound microscopes utilize multiple lenses: the objective lens near the specimen and the ocular lens for viewing, creating a combined magnification effect.
The focal point is where light rays converge through a convex lens; focal length is the distance from the lens center to the focal point.
Shorter focal lengths correspond to higher magnification and require closer proximity to the object being viewed.
Microscopy depth of field decreases with increased magnification; focusing must occur through the object at high magnifications.

Proper Use of the Microscope

Always carry the microscope upright with both hands to prevent damage.
Place it carefully on a stable surface, avoiding edges and sliding across tables.
Electric cords should be positioned to prevent tripping hazards.
Clean lenses only with lens paper; avoid other materials which can scratch the lenses.
Begin with the stage lowered and the lowest power objective lens; gradually increase light intensity after turning on the illuminator.
Coarse focus should only be used on low power; always lower the stage to focus the specimen when viewing through the ocular.
Fine focus is critical for sharpening the image; ensure low power focus before increasing magnification.
Prioritize centering the specimen before switching to a higher power objective lens; make sure not to contact the slide during changes.
Return to low power and move the objective away from the slide before removal.
After use, clean lenses, coil cords, cover the microscope, and store it properly.

Estimating Object Size

Use a ruler method for size estimation, best when objects are aligned vertically with the stage.
Focus on an object and position a ruler against the stage edge at the same eye distance.
Open the other eye to compare the object with the ruler and measure the object's length in cm or half cm.
Calculate actual size by dividing the measured length by total magnification (Actual Length = Measured Length / Total Magnification).

Microscope Practice

Estimate the length of one square of graph paper using the above method.
Practice focusing on an amoeba at various power levels (low, medium, high).

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Description

This quiz focuses on the essential aspects of microscopy, including the parts and functions of a compound microscope and proper procedures for examining specimens. You will also learn about safety measures associated with microscope usage. Perfect for reinforcing your understanding of microscopy in relation to prokaryotic cells.