Question

Phase contrast microscope is
(a)Based on the scatter light and using the darkfield condenser
(b)Used for the study of living cells
(c)Related to retardation and thickness of the object
(d)The best method for studying non-living ultra-structures

Answer 1

Hint: It is used for the study of ultra-structures that are not visible to the naked eyes. The compounds are generally studied by preparing a culture media and these culture media should be made sterile before use so as to not cause any microscopic errors.

Complete answer:
Phase-contrast microscopy is an optical microscopy technique that converts phase shifts in the light passing through a transparent specimen to changes in the brightness of the image. Phase changes themselves are invisible but become apparent when seen as differences in brightness.
 Phase-contrast microscopy is of particular interest in biology. It shows several cellular structures invisible to the bright-field microscope, as exemplified in the figure. These structures were made evident by staining to earlier microscopists, but this required additional preparation and death of the cells.
The phase-contrast microscope has made it possible for biologists to study living cells and how they proliferate via cell division. It is one of the few methods available for quantifying cellular structure and components that do not use fluorescence.

Additional Information: Based on the scatter light and using the dark field condenser- Dark-field microscopy (also known as dark-ground microscopy) describes methods of microscopy, both in light and electron microscopy, which remove the unbroken beam from the image. As a result, the area around the specimen (i.e. where there is no specimen to spread the beam) is usually dark.
The best method for studying non-living ultra-structures- Electron microscopy is used when the highest resolution is needed and the living state can be overlooked. The images produced by the electron microscope reveal the ultrastructure of the cells.
So, the correct answer is ‘used for the study of living cells’.

Note: After its discovery in the early 1930s, phase-contrast microscopy proved to be such innovation in microscopy that its inventor Frits Zernike was awarded the Nobel Prize in Physics in 1953.