Lab 1: Microscopes

Biology

What is magnification?

How many times larger an image appears compared with the actual object.

What is resolution?

The ability to distinguish fine details and nearby points as separate.

What is the limit of resolution?

The minimum distance at which two points can be distinguished as separate.

Does a smaller limit of resolution mean better resolution?

Yes. Points that are closer together can be distinguished.

What is the field of view?

The circular area visible through the eyepieces.

What happens to the field of view as magnification increases?

It becomes smaller: you see less of the specimen.

What is working distance?

The distance between the objective lens and the specimen.

What happens to working distance with higher-power compound objectives?

It decreases: the objective is closer to the specimen.

What are the two main branches of microscopy?

Light microscopy and electron microscopy.

What does light microscopy use?

Visible light.

What does electron microscopy use?

A beam of electrons.

Which branch of microscopy can be used to view living specimens?

Light microscopy.

What is the main advantage of electron microscopy?

Higher magnification and resolution.

What is the main biological limitation of electron microscopy in this lab?

It cannot be used to observe living specimens.

What light-microscopy values are given in the lab introduction?

1,000× magnification and 200 nm resolution.

What electron-microscopy values are given in the lab introduction?

100,000× magnification and 0.1 nm resolution.

What is the maximum magnification of the lab compound microscope?

400×.

What is the maximum magnification of the lab stereomicroscope?

50×.

Which microscope is best for observing thin cellular specimens at higher magnification?

The compound light microscope.

Which microscope is best for dissecting a small insect?

The stereoscopic or dissecting microscope.

Why does a stereomicroscope produce a 3D view?

Two separate optical pathways provide slightly different images to each eye, allowing depth perception.

Which microscope has a larger working distance?

The stereoscopic microscope.

How does the lab compound microscope focus mechanically?

By moving the stage up and down.

How does the lab stereomicroscope focus mechanically?

By moving the head up and down.

What controls magnification on a stereomicroscope?

The zoom knob.

What is the function of the arm?

It supports the microscope body and is held during transport.

What is the function of the ocular or eyepiece?

It further magnifies the objective image by 10×.

What is the function of the objective lenses?

They produce the initial magnified image of the specimen.

What is the function of the revolving nosepiece?

It allows you to switch objective lenses.

What is the function of the condenser?

It collects and concentrates light onto the specimen.

What is the function of the light source?

It provides illumination.

What is the function of the diaphragm lever?

It changes the aperture, affecting light, contrast and resolution.

What is the function of the stage?

It supports the microscope slide.

What is the function of the mechanical stage or slide holder?

It holds and moves the slide along the X and Y axes.

What is the function of the brightness control knob?

It adjusts light intensity.

What is the function of the ON/OFF switch?

It turns illumination on and off.

What is the function of the coarse focus knob?

It moves the stage in large increments for initial focusing. Use it only with the 4× objective.

What is the function of the fine focus knob?

It makes small adjustments for precise focus and can be used with any objective.

In the lab figure, which part is number 2?

The ocular or eyepiece.

In the lab figure, which part is number 7?

The condenser.

In the lab figure, which part is number 12?

The stage.

In the lab figure, which part is number 13?

The mechanical stage.

According to the lab component table, which part is number 18?

The ON/OFF switch. One quiz correction conflicts with this table.

In the lab figure, which part is number 19?

The coarse focus knob.

In the lab figure, which part is number 20?

The fine focus knob.

How should you carry a microscope?

With two hands: one holding the arm and one supporting the base.

Which objective must you start with?

The 4× scanning objective.

Why should you start with the 4× objective?

It provides a wide field of view and reduces the risk of collision with the slide.

How many circles should you see after adjusting the ocular distance?

One circle of light.

Which focus knob is used first at 4×?

Coarse focus, followed by fine focus.

With which objective can you use coarse focus in this lab?

Only with the 4× objective.

Which focus knob should you use with the 10× and 40× objectives?

Fine focus only.

Why is coarse focus unsafe with the 10× and 40× objectives?

Large stage movements may make the slide hit the nearby objective.

What should you do before switching to a higher-power objective?

Focus and center the region of interest.

What should you do if you lose the image at high magnification?

Return to 4×, locate, focus and center the specimen again.

How should you switch objectives?

Rotate the revolving nosepiece instead of grabbing the objective lenses.

What is the correct order for preparing the letter e wet mount?

Place the letter right side up on a clean slide, add water, and lower a coverslip at about 45°.

Why should you lower the coverslip at about 45°?

To minimize trapped air bubbles.

Why use a toothpick to lower the coverslip?

To avoid finger oils and contamination.

How can you add water beneath a coverslip?

Place a drop at the edge; capillary action draws it underneath.

How is the image oriented in a compound microscope?

Upside down and reversed left to right relative to the specimen.

If the slide moves right, which way does the image move?

Left.

If the slide moves away from you, which way does the image move?

Down.

How do you calculate total magnification?

Multiply ocular magnification by objective magnification.

What is the total magnification with a 10× ocular and a 4× objective?

40×.

What is the total magnification with a 10× ocular and a 10× objective?

100×.

What is the total magnification with a 10× ocular and a 40× objective?

400×.

Which objective should be selected before removing a slide?

The 4× objective.

Where should the stage be positioned for storage?

All the way down.

Can you store the microscope with a slide in place?

No. Remove the slide before storage.

What should you use to clean the lenses?

The supplied lens tissue and lens cleaner.

Which nosepiece position is used for storage?

An empty slot if available; otherwise the shortest 4× objective.

Which way should objectives and oculars face in the cabinet?

Toward the back of the cabinet.

Can you return your microscope to any free cabinet space?

No. Use the numbered space assigned to that microscope.

What should you do with the light before storage?

Turn brightness to minimum, switch off and unplug.