Phase Contrast microscopes create images, without staining, by using refraction and interference caused by structures in a specimen. Structures that refract light appear dark against a bright background of unrefracted light. Structures that differ in refractive indexes will vary in levels of darkness.

Phase Contrast Microscopes

After passing through either the specimen or an empty space, the light waves are recombined, and the specimen's alter the interference patterns formed. This produces high-contrast, 3-D images of living microorganisms. 

Differential Interference Contrast Microscopes (DIC)

Light waves can interfere in two manners: in phase or out of phase. In phase light waves add their amplitudes (heights), whereas out of phase waves cancel each other out. 

How we perceive light depends on how it is reflected, refracted, and absorbed or transmitted through a material medium.


Light Perception

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Microscopy relies mostly on refraction, which is the change in direction of a light ray because it crosses into a new material.

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