Question

In a way to examining the cellular organelles in the slide and study ribosomes. Answer the following :

(Please do not answer by hand written,i cant understand)

1.What type of microscope is used to view these organelles?

2.Explain principle and working mechanism of type specific microscope which doesn’t penetrate the organelles but measures the size and structure

Answer 1

1. .What type of microscope is used to view these organelles?

Ans. A light microscope is usually suffiecient to study shape of the cell and its nuclues but for studying other cell organelles an electron microscope is required. Structures like ribosomes can be viewed only with electron microscopes.

2. Explain principle and working mechanism of type specific microscope which doesn’t penetrate the organelles but measures the size and structure?

There are two types of electron microscopes utilised to view cells and organelles in a better way and they are 1. Transmission electron microscpe 2. Scanning electron microscope.

Transmission electron microscope allows the electron beam to pass through the organelles for studying their internal structure where as scanning electron microscope scans only the the surface of the sample with the electron beam and produces information about surface tonography and composition of the sample.

Principle and working mechanism of Scanning Electron Microscope:

PRINCIPLE: The basic principle of SEM is that an electron beam is generated from a suitable source like field emission gun or tungsten filament. This electron beam is accelerated through high volatage system and passed through appertures and electron magnetic lenses to produce a thin beam of electrons, which scan the surface of the specimen. Electrons are emitted  from the specimen by the action of scanning electron beam and are collected by the suitable positioned detector.

Working of Scanning Electron Microscope:

• When the tungsten wire is heated the electron gun produces a beam of electrons
• The beam is accelerated by high voltage system and it travels through electromagnetic filed and lenses which focus the beam on sample.
• Secondary electrons, back scattered electrons and X-rays are produced when the electron beam touches the surface of the sample.
• The secondary electrons are collected by SED(secondary electron detector) and converted into a signal that is sent to screen to produce final image.
• Back scattered electrons and X-rays are collected by additional detectors to produce corresponding images.