Overview
This lecture explains why immersion oil is used with oil immersion objectives on microscopes, focusing on light refraction and image clarity at high magnifications.
Reflection vs. Refraction
- Reflection occurs when light bounces off a surface without passing through it.
- Refraction is when light passes through a medium and changes direction.
Refraction in Microscopy
- As light passes through the glass slide and specimen, it can refract, bending away from a straight path.
- At lower magnifications, some light loss due to refraction is not significant.
- At higher magnifications, losing light rays to refraction reduces image brightness and clarity.
Role of Immersion Oil
- Immersion oil is used with oil immersion objectives to reduce light refraction.
- The refractive index of immersion oil matches that of glass.
- With oil, light travels from the slide, through the oil, directly into the objective, minimizing bending.
- More light enters the objective, resulting in a clearer, brighter image.
- Using a high-power objective without immersion oil produces blurry images due to lost light.
Key Terms & Definitions
- Reflection — Light bouncing off a surface without penetrating it.
- Refraction — The bending of light as it passes through different media.
- Refractive Index — A measure of how much a substance bends light.
- Immersion Oil — A mineral oil with a refractive index similar to glass, used to improve microscope image quality at high magnification.
Action Items / Next Steps
- Practice using immersion oil with high-power microscopy objectives.
- Review procedures for cleaning and applying immersion oil to microscope slides.