Light Microscopy Lecture

Introduction to Light Microscopy

• Light microscopy uses light to visualize specimens.
• Students often question the relevance of physics in biology, specifically wavelength of light.

Light as an Electromagnetic Wave

• Light is an electromagnetic wave with different frequencies.
• Low Frequency Light:
  • Peaks and valleys occur less frequently.
  • Example: Red light (considered low frequency)
• High Frequency Light:
  • Peaks and valleys appear more quickly.
  • Example: Violet light (considered high frequency)
• Green light falls somewhere in the middle.

Wavelength of Light

• Definition: Distance between peaks or valleys in a wave.
• Symbolized as lambda (λ).
• Red Light:
  • Wavelength: 700 nanometers (low frequency)
• Violet Light:
  • Wavelength: 400 nanometers (high frequency)

Importance of Wavelength in Biology

• Understanding wavelengths is crucial for visualizing specimens in microscopy.
• Reflection of Light:
  • Light must hit and reflect off a specimen to be seen.
• Microscopy:
  • Certain cellular structures are too small to be visualized with light.

Application in Microscopy

• Chloroplasts:
  • Large organelles, about 2000 nanometers.
  • Can be seen with a light microscope using red light because they reflect the light.
• Ribosomes:
  • Small organelles, about 23 nanometers.
  • Cannot be seen with a light microscope.
  • Red light or violet light passes through ribosomes without reflection.

Key Takeaways

• Understanding light frequencies and wavelengths is essential for using light microscopy effectively.
• Large organelles like chloroplasts can be visualized with light microscopy, while small structures like ribosomes cannot.