The focal length, or focal distance, is the spatial distance measured from the center of an optical lens to its focal point. It is affected by the curvature of the lens; more curvature creates image points closer to the lens and produces a larger image when in focus. Additionally, for a given curvature, placing an object closer to the lens moves the focal points farther from the lens, requiring manipulation of distances between the object, lens, and screen to create a focused image.

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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

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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.

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Resolution is how clear an image appears. It is impacted by wavelength of light and a lens’s capability of collecting light. 

Resolution

The image point, also referred to as the focus, is the single location where an optical lens collects and refracts all the striking light to meet.

Image Point

The focal point is the specific image point where all light entering a lens parallel to its axis converges after refraction. For a convex lens, this point is located past the lens where the bent light rays meet; for a concave lens, it is the point on the originating side where the backwards linear paths of the scattered light beams intersect.

Focal Point

A convex lens is an optical lens with a center bulge that refracts incoming light to converge at a focal point past the lens. It is commonly used to magnify objects because it is capable of focusing at a closer range than the human eye, thereby producing a larger image.

Convex Lens

A concave lens is an optical lens that curves inward on either side and refracts incoming light outwards, away from the center of the curve. Along with mirrors, these lenses are often used in microscopes to redirect the path of light.

Concave Lens

Artificial lenses, such as contact lenses, glasses, or microscopic lenses, are devices placed in front of the eye to manipulate the final image that is perceived. They function by focusing incoming light before it is further focused by the natural lens of the human eye, which alters the resulting image on the retina by making it appear larger or clearer.

Artificial Lenses

Focal Length

Magnification is the ability of a lens to enlarge the image of an object compared to the real object. For example, a magnification of $${}10	imes$$ indicates that the image appears $${}10$$ times the size of the object as viewed with the naked eye.

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