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  2. Parfocal lens - Wikipedia

    en.wikipedia.org/wiki/Parfocal_lens

    Zoom lenses (sometimes referred to as "true" zoom) are ideally parfocal, in that focus is maintained as the lens is zoomed (i.e., focal length and magnification changed), which is convenient and has the advantage of allowing more accurate focusing at maximal focal length then zooming back to a shorter focal length to compose the image. [1]

  3. Oil immersion - Wikipedia

    en.wikipedia.org/wiki/Oil_immersion

    The resolution of a microscope is defined as the minimum separation needed between two objects under examination in order for the microscope to discern them as separate objects. This minimum distance is labelled δ. If two objects are separated by a distance shorter than δ, then they will appear as a single object in the microscope.

  4. Birefringence - Wikipedia

    en.wikipedia.org/wiki/Birefringence

    Birefringence is utilized in medical diagnostics. One powerful accessory used with optical microscopes is a pair of crossed polarizing filters. Light from the source is polarized in the x direction after passing through the first polarizer, but above the specimen is a polarizer (a so-called analyzer) oriented in the y direction. Therefore, no ...

  5. Optical microscope - Wikipedia

    en.wikipedia.org/wiki/Optical_microscope

    The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects. Optical microscopes are the oldest design of microscope and were possibly invented in their present compound form in the 17th century.

  6. Hailee Steinfeld Encourages Women to 'Give Breasts the ... - AOL

    www.aol.com/hailee-steinfeld-encourages-women...

    Hailee Steinfeld and Wanda Sykes costar in a Super Bowl ad encouraging women to prioritize their breast health . In PEOPLE's exclusive first look, Steinfeld encourages viewers to "give breasts the ...

  7. Dark-field microscopy - Wikipedia

    en.wikipedia.org/wiki/Dark-field_microscopy

    Diagram illustrating the light path through a dark-field microscope. The steps are illustrated in the figure where an inverted microscope is used. Light enters the microscope for illumination of the sample. A specially sized disc, the patch stop (see figure), blocks some light from the light source, leaving an outer ring of illumination. A wide ...

  8. Quizlet - Wikipedia

    en.wikipedia.org/wiki/Quizlet

    Quizlet's primary products include digital flash cards, matching games, practice electronic assessments, and live quizzes. In 2017, 1 in 2 high school students used Quizlet. [ 4 ] As of December 2021, Quizlet has over 500 million user-generated flashcard sets and more than 60 million active users.

  9. Microscopy - Wikipedia

    en.wikipedia.org/wiki/Microscopy

    Antonie van Leeuwenhoek (1632–1723). The field of microscopy (optical microscopy) dates back to at least the 17th-century.Earlier microscopes, single lens magnifying glasses with limited magnification, date at least as far back as the wide spread use of lenses in eyeglasses in the 13th century [2] but more advanced compound microscopes first appeared in Europe around 1620 [3] [4] The ...