1/14/26- CH 3

Course Administration and Attendance

  • Reminder for students who haven't attended to sign in as attendance is crucial for the course.

  • Note on dropping the course: If students consider dropping, deadlines for that are approaching.

  • Upcoming job call announcement: Scheduled for tomorrow at 4:00 PM in Ed Connelly's building. Speaker: Dr. Mori, a cell morphologist, presenting on a topic relevant for extra credit.

Current Health Issues

  • Discussion of the bird flu issue in the Midwest, specifically noting a significant human flu variant that is causing concern.

  • Notable case of measles reported in South Carolina: 124 new cases mainly in Spartanburg.

  • Accurate reporting and source verification: The speaker emphasizes going straight to credible sources like the Department of Public Health rather than media that may copy-paste information without proper context.

    • South Carolina Department of Public Health report:

    • Total reported cases: 434

    • Age breakdown of measles cases:

      • 105 cases: Age 5 and under

      • 287 cases: School-age

      • 36 cases: Age 18 and over

    • Vaccination status of cases:

      • 378: Not vaccinated

      • 3: Partially vaccinated

      • 47: Vaccinated

Lecture Content: Microscopy

Key Concepts of Microscopy

  • Resolution:

    • Definition: Smallest distance between two points that can be distinguished.

    • Discussion of its synonym, clarity, and its importance alongside magnification.

  • Magnification vs. Resolution:

    • Conclusion: Magnification without resolution is ineffective.

    • Mathematical expression related to resolution: R=racext0.5imesextwavelengthextNumericalApertureR = rac{ ext{0.5} imes ext{wavelength}}{ ext{Numerical Aperture}}

      • Wavelength: A factor that can affect resolution. Typically uses white light.

  • Numerical Aperture (NA):

    • Definition: The range of angles that light can enter the lens.

    • Determinants of NA: Lens diameter and working distance (distance of lens from sample).

    • Mathematical form: NA=extnimesextsine(extalpha)NA = ext{n} imes ext{sine}( ext{alpha}) where alpha is 1/2 of the objective.

Improving Resolution

  • Methods to enhance resolution:

    • Decrease wavelength (using UV light).

      • Caution: UV light can damage eyes, impractical for direct observation.

    • Use of a condenser: Increases light focus on sample.

    • Oil immersion: Increases NA to 1.5 (from air's index of 1).

    • Use of immersion oil between lens and cover slip to improve light transmission: Oil reduces bending and improves light collection.

Microscopy Techniques Comparison

Bright Field Microscopy

  • Light shines directly through the sample, causing the sample to appear darker.

  • Mainly used with stained cells to enhance contrast.

Dark Field Microscopy

  • Light does not shine directly through the specimen, making it useful for visualizing fine structures, like flagella.

  • Provides clearer images by utilizing peripheral light that’s scattered off the specimen against a dark background.

  • Can visualize very fine structures better than bright field.

Phase Contrast Microscopy

  • Utilizes two light rays that are slightly out of phase to enhance contrast without staining.

  • Enhances visibility of thin samples like living tissues.

  • Light wave interference is used to manipulate light for better imaging.

Differential Interference Contrast (DIC) Microscopy

  • Advanced technique using polarized light and prisms that shear light to enhance