Optical Instruments and Human Eye

Fluorescent microscope is a modification of ultraviolet microscope which was made by Coons in 1945. The instrument uses long wave ultraviolet rays for illumination. It has complementary filters which allow the viewer to observe directly with the eyes. The microscope is useful in detecting those components which show autofluorescence, e.g., chlorophylls, collagen fibrils, vitamin A, etc. Others can be made fluorescent by coating with fluorochrome dyes like acridine orange and coriphosphine and minerals, eg., proteins, lipids, starch, glycogen, cellulose etc. The light emitted by them is red, orange, yellow, or green against dark field, it is called as secondary fluorescence. The technique is also useful in diagnosis of viruses, bacteria and protozoans. Immunofluorescent antibody labelling techniques is used in diagnosis of specific molecules like antigens and antibodies, it involves conjugating specific fluorochromes with specific antibodies.

The most powerful lens of the light microscope is the 100X oil immersion objective because light is refracted every time it passes through a medium with a different refractive index, the quality of the image is reduced with each passage. Thus, by reducing the number of such passages to a minimum, the clarity, brilliance and resolving power is preserved. Immersion oil has been formulated so that it has a refractive index identical to that of glass. Thus, two changes in refractive index can be eliminated by placing a drop of immersion oil on the specimen, and immersing the 100X oil immersion objective directly into the drop. 

A microscope is an instrument used to see objects that are too small to see by naked eyes. It consists the lens which magnifies the image of cells. 

Resolving power is the ability to distinguish two close objects as distinct. It is calculated by the formula 0.61 wavelength/ numerical aperture, where  numerical aperture is the light collecting ability of lens. It is clear that resolving power will be more if wavelength is less and numerical aperture is more. Thus, the correct answer is option A.

Total magnification is calculated as (ocular lens magnification) * (objective lens magnification). With an ocular lens of 10x, the possible total magnifications are 10*10=100x, 10*20=200x, 10*30=300x, and 10*43=430x. 10x is not possible as the minimum magnification is 100x.

Antonie van Leeuwenhoek, known as the father of microbiology, developed simple microscopes with single lenses that could achieve magnifications of up to 300 times.

Both Scanning Electron Microscopes (SEM) and Transmission Electron Microscopes (TEM) utilize electron beams to image specimens at high resolution.

The Leeuwenhoek microscope was a simple single lens device but it had greater clarity and magnification than compound microscopes of its time. Designed by a Dutchman, Antony van Leeuwenhoek, the microscope was completely handmade including the screws and rivets.

A plano-concave mirror is used in classroom microscopes to reflect light from an external source onto the specimen, helping to focus the light appropriately.

The standard oil immersion objective lens used in light microscopy typically provides a magnification of 100x.

In electron, fluorescent, and ultraviolet microscopes, the light or radiation used is often invisible to the human eye, requiring a fluorescent screen or photographic plate for detection.

Ultraviolet light is invisible to the human eye, so direct observation through an eyepiece is not possible; the image must be captured on a photographic plate or digital sensor.

Fluorescence microscopy relies on the excitation of fluorophores using high-energy light, typically UV or blue light, to emit visible light. Therefore, it utilizes both UV rays for excitation and visible light for the resulting emission.

A stop is an opaque object that blocks the central light when placed underneath the stage condenser. This also causes light to scatter in all azimuths, resulting in a cone of light that allows for dark field observation.

Fluorescence microscopes use UV or blue light to excite samples and require specific filters (like excitation and emission filters) to isolate the wavelengths of light, which are often referred to as complementary filters.