Optical (Light) Microscope
Magnifies particles so their size, shape and crystal habit can be seen and measured with a calibrated eyepiece graticule or camera. Used for particle size, morphology and identification checks.
- Pharmaceutical
- Microbiology
- Materials
- Food
- Forensics
- Education
Test your Optical microscope knowledge
Multiple-choice questions
Pick an answer to see whether you are right and why.
Q1. A 40× objective with a 10× eyepiece gives a total magnification of:
basicQ2. What is a stage micrometer used for?
basicQ3. Under crossed polarisers, crystalline particles usually:
intermediateQ4. Microscopy particle sizing gives a distribution weighted by:
intermediateQ5. Feret's diameter is:
intermediateQ6. The best practical resolution of a light microscope with oil immersion is about:
advanced
Viva questions
Think of your answer first, then open it to compare.
1. Why must the graticule be calibrated for each objective?
The graticule sits in the eyepiece, so the real distance represented by one division changes with the objective's magnification. Each objective is calibrated against a stage micrometer and the factor recorded.
2. How do you avoid bias when sizing particles by microscopy?
Scan fields in a fixed pattern rather than choosing attractive particles, measure a set number of particles, use a consistent size definition (e.g. Feret's diameter in one direction), and calibrate the graticule. Image analysis software reduces analyst-to-analyst differences.
3. How is microscopy used alongside laser diffraction?
Microscopy shows particle shape and whether agglomerates are present. This helps choose dispersion conditions and explain laser diffraction results, especially for needles or plates where the equivalent-sphere size can mislead.
Keep every Optical microscope in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.