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Using a Microscope

Middle schoolBiologyA synthetic bright-field specimen with objective-based field diameter, a numerical-aperture resolution estimate and illustrative defocus

Turn the orange focus control and switch objectives. Move the slide with the stage controls.

3D

Drag the apparatus to adjust it. Drag the background to rotate. Scroll to zoom.

Synthetic microscope specimen

40× · 4500 µm

Measurement notebook

Change the setup, test a prediction and save the result. Up to 12 snapshots are kept.

About this experiment

Operate a three-dimensional microscope while inspecting a synthetic eyepiece image. Switch objectives, move the specimen and refocus to connect the instrument controls with the observed field. Compare total magnification with resolution and depth of field instead of assuming a larger image always reveals more detail.

Learning goals

  • Relate objective and eyepiece powers to total magnification.
  • Compare field diameter, resolution and depth of field as numerical aperture changes.
  • Use the scale bar to interpret specimen size and recognize synthetic image limitations.

How to use it

  1. 1Start with the 4× objective, locate cell walls and move the slide horizontally and vertically.
  2. 2Switch to 40×, move focus away from the specimen plane and restore focus.
  3. 3Reduce aperture and compare the resolution and depth-of-field estimates.
  4. 4Change eyepiece power without changing the objective, record the optical measurements and save a view.

The model

Total magnification
Resolution and approximate depth of field

Assumptions

  • The specimen is a deterministic drawing of onion or leaf epidermis, not a photograph or a diagnostic sample. Blur and brightness are illustrative.
  • Field diameter is 18 mm divided by objective power. All eyepieces are assigned the same 18 mm field number. Wavelength is fixed at 0.55 µm.
  • Resolution is estimated by 0.61 wavelength divided by numerical aperture; depth of field uses wavelength divided by aperture squared. Aberrations, immersion media, optical sectioning and quantitative image formation are excluded.

Try this in class

  1. Q1Why does a higher-power eyepiece not improve the objective-based resolution estimate?
  2. Q2Why can closing the aperture make a defocused specimen look clearer while reducing resolution?

Frequently asked questions

Is the image suitable for identifying real tissue?

No. It is a synthetic teaching specimen with deliberately simplified structures.

Why does eyepiece power change magnification but not the displayed field diameter?

The model fixes the eyepiece field number. Under that assumption specimen field diameter depends only on objective power.