Phosphorescence is a process where a material absorbs photons and emits lower-energy photons following a delay. Because of this delayed emission, phosphorescent materials, such as those used in glow-in-the-dark plastics, can continue to emit light even after the initial energy source has been removed.

Phosphorescence

Electromagnetic radiation (EMR) is a type of energy that exists all around us and is delivered as elementary particles called photons. Its different forms, such as visible light, microwaves, X-rays, and radio waves, are classified on the electromagnetic spectrum and are defined in terms of their wavelength and frequency.

Electromagnetic Radiation (EMR)

Methods of preparation to allow us to view and distinguish different cells and their structures that were otherwise translucent through the use of ionic salts in stains/dyes. 

Staining 

Chromophores are pigments that absorb and reflect specific wavelengths of light, causing different colors to interact with them in distinct ways. In microscopy, these pigments are frequently added to specimens artificially through the use of stains, which serves to enhance the contrast and resolution of the resulting image.

Chromophores

Fluorochromes are fluorescent chromophores capable of absorbing energy from a short-wavelength excitation light source and emitting it as longer-wavelength visible light. They can be naturally fluorescent substances, like chlorophylls, or added fluorescent stains—such as Texas red, fluorescein isothiocyanate (FITC), 4',6'-diamidino-2-phenylindole (DAPI), and acridine orange—used to create contrast in fluorescence microscopy.

Fluorochromes

Contrast refers to the visible differences between the parts of a specimen. Even when a microscope has high resolution, it can be difficult to distinguish small structures because many microorganisms are relatively transparent. To improve visibility, contrast can be increased by utilizing different features of light or electrons in microscopes, or by applying dyes that bind selectively to certain structures.

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Microbes are too small to be seen with the naked eye, so humans have developed techniques and technology to observe and study them.

Visualizing Microbes

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

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


Light Perception

Microscopes are fundamental tools in microbiology that produce magnified images of specimens generally too small to be seen with the naked eye. By manipulating the physical properties of light—such as contrast, size, and color—microscopes allow researchers to examine microbial cells in high detail. This capability is crucial for both clinical and research applications, including the identification of specific microbial species and the diagnosis of diseases. Before microscopes, theories about microorganisms were strictly hypothetical.

Microscopes

An optical lens is an object with a curved boundary, functioning similarly to a collection of prisms, that collects striking light and refracts it so that it all meets at a single focus or image point. Lenses operate on the principle of refraction; when light crosses into the lens material (which typically has a higher refractive index than its surroundings), its direction turns closer to perpendicular to the boundary, bending more toward a normal.

Optical Lenses

Contrast

In clinical settings, light microscopes are frequently used to observe microorganisms. Because most cells and microbes lack color and contrast in their natural state, specimens must be artificially treated to detect important cellular structures. The two basic types of preparation used to view specimens with a light microscope are wet mounts and fixed specimens.

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