What is Compound microscope: Definition and 21 Discussions

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. Basic optical microscopes can be very simple, although many complex designs aim to improve resolution and sample contrast.
The object is placed on a stage and may be directly viewed through one or two eyepieces on the microscope. In high-power microscopes, both eyepieces typically show the same image, but with a stereo microscope, slightly different images are used to create a 3-D effect. A camera is typically used to capture the image (micrograph).
The sample can be lit in a variety of ways. Transparent objects can be lit from below and solid objects can be lit with light coming through (bright field) or around (dark field) the objective lens. Polarised light may be used to determine crystal orientation of metallic objects. Phase-contrast imaging can be used to increase image contrast by highlighting small details of differing refractive index.
A range of objective lenses with different magnification are usually provided mounted on a turret, allowing them to be rotated into place and providing an ability to zoom-in. The maximum magnification power of optical microscopes is typically limited to around 1000x because of the limited resolving power of visible light. The magnification of a compound optical microscope is the product of the magnification of the eyepiece (say 10x) and the objective lens (say 100x), to give a total magnification of 1,000×. Modified environments such as the use of oil or ultraviolet light can increase the magnification.
Alternatives to optical microscopy which do not use visible light include scanning electron microscopy and transmission electron microscopy and scanning probe microscopy and as a result, can achieve much greater magnifications.

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  1. B

    I What is really happening in collimation of rays?

    Ok so if an object is placed at the focal point of a convex lens, it will have it's rays collimated -- which I assumed to mean that all rays would end up parallel to each other. But then, I saw this diagram of a simple compound microscope from Hecht "Optics" 5th ed: And I noticed that all...
  2. B

    I Compound Microscope System: Magnification Power Explained

    Ok so for a compound microscope system like the one below, Magnification power is ## MP = M_T * M_A ##. My present understanding is that ##M_T## refers to the magnification by height ratios of the object through L1, and ##M_A##, in this case, refers to the ratio of unaided and aided angles of...
  3. S

    B What is the Length of a Compound Microscope?

    If we say "length of microscope", which distance does it refer to? Is it: a) the tube length (L), which is the distance between the focal point of objective and focal point of eye piece lens OR b) the distance (d) between objective and eye piece lens Thanks
  4. Wrichik Basu

    B Which ray diagram is correct for a Compound microscope?

    Here are two ray diagrams for compound microscope, the first one proposed by the book, and the second one recommended by the teacher: In the first image, the light rays form a real image A'B', which becomes the virtual object for the eyepiece. See, the original rays are carried forward to...
  5. moenste

    Distance of the final image in a compound microscope

    Homework Statement A compound microscope has an objective of focal length 12 mm and an eyepiece of focal length 50 mm. The lenses have a separation of 90 mm and an object of height 0.3 mm is placed 15 mm from the objective. Calculate: (a) the distance of the intermediate image from the...
  6. A

    Compound Microscope: Focal Length of Objective Lens vs Eye Piece

    Why is the focal length of the objective lense is less than that of the eye piece in a compound microscope?
  7. P

    Solving Compound Microscope Lens Length Problem

    Homework Statement The barrel of a compound microscope is 15.9 cm in length. The specimen will be mounted 1.17 cm from the objective, and the eyepiece has a 5.00 cm focal length. Determine the focal length of the objective lens.Homework Equations I am using the mirror equation. The Attempt at...
  8. R

    Compound Microscope Magnification @ Infinity

    is magnification negative for a compound microscope at infinity
  9. A

    Why don't compound microscopes use an erecting lens like terrestrial telescopes?

    I read that in terrestrial telescope there is an erecting lens whose function is to erect the inverted image formed by objective lens so that final image formed by eyepiece is also erect.there is no need of erecting lens in astronomical telescope because astronomical bodies are symmetrical in...
  10. M

    Compound Microscope, Ray Diagram Mistakes.

    I noticed that the ray diagram for the "how the compound microscope works" and "how the telescope works" is wrong in my government sanctioned physics textbook(and countless other books and websites!) The diagram printed was this- Name: Physics Standard XI Printed by: Maharastra State Board of...
  11. C

    Compound microscope focal length

    Homework Statement The barrel of a compound microscope is 15 cm in length (distance between lenses). The specimen will be mounted 1.0 cm from the objective, and the eyepiece has a 5.0-cm focal length. Determine the focal length of the objective lens. Known: f2=5cm, L=15cm, do1=1cm...
  12. R

    Functioning of a compound microscope

    "The diameter of the eyepiece is greater than that of the objective. This helps to collect more light and gives a brighter image" I thought that increasing the aperture of a lens doesn't increase the brightness of a virtual image. Yes, it will increase the brightness of a real image caught on...
  13. X

    Finding focal lens of compound microscope

    The question is: A microscope has a 12.0 X eyepiece and a 59.0X objective lens 20.0cm apart. Calculate (a) the total magnification, (b) the focal length of each lens, and (c) where the object must be, for a normal relaxed eye to see it in focus. I have solved (a) easily through M = moMe...
  14. D

    Compound microscope (position of the object)

    Homework Statement A microscope has a 1.6 cm focal-length eyepiece and 0.81 cm objective. Assume a relaxed normal eye. (a) Calculate the position of the object if the distance between the lenses is 16.0 cm. _____ cm (from the objective) (b) Calculate the total magnification. ________...
  15. M

    Homemade Compound Microscope Problem

    1. Homework Statement A Homemade compound microscope has, as objective and eyepiece, thin lenses of focal lengths 1cm and 3cm, respectively. An object is situated at a distance of 1.20cm from the objective. If the virtual image produced by the eyepiece is 25cm from the eye, compute (a.) the...
  16. D

    Compound Microscope Homework: Angular Magnification & Object Distance

    Homework Statement A microscope has an eyepiece that gives an angular magnification of 5.25 cm for a final image at infinity and an objective lens of focal length 1.45 cm. The tube length is 16.1 cm. a - What is the transverse magnification due to the objective lens alone? b - what is the...
  17. A

    What Does the Negative Sign Indicate in the Mo Formula on HyperPhysics?

    Homework Statement At this site http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/micros.html , what does the negative sign indicate in the Mo formula? Homework Equations On website The Attempt at a Solution My guess is that either L or Fo are negative, but a negative magnification...
  18. A

    Understanding the Negative Sign in Microscope Mo Equation | HyperPhysics

    I came across http://hyperphysics.phy-astr.gsu.edu/hbase/geopt/micros.html Any idea what the negative sign indicates in the mo equation?
  19. E

    Compound Microscope Homework: Magnifying Power & Lens Separation

    Homework Statement A Homemade compound microscope has, as objective and eyepiece, thin lenses of focal lengths 1cm and 3cm, respectively. An object is situated at a distance of 1.20cm from the objective. If the virtual image produced by the eyepiece is 25cm from the eye, compute (a.) the...
  20. M

    Compound Microscope: Solving for Objective Focal Length

    A compound microscope has the objective and eyepiece mounted in a tube that is 18.0 cm long. The focal length of the eyepiece is 2.08 cm, and the near-point distance of the person using the microscope is 25.0 cm. If the person can view the image produced by the microscope with a completely...