Question

a) Describe, using a schematic/diagram of your own creation, how an electron microscope changes from low magnification to high magnification.

b) Why is it preferable to image a conductive surface in an SEM?

c) Is the conductivity of the sample as critical in a TEM as it is in an SEM? Why or why not?

Answer 1

(a) The electron microscope's magnification depends on the wavelength of the electron beam being used in the microscope, as the wavelength of the microscope decreases (Energy of the beam increases) the magnification also increases. This change in wavelength is made by changing the potential through which the electron is accelerated or changing a parameter in other mechanisms through which we can increase the energy of the electron. The electromagnetic lenses which is used to focus the beams can also be changed to change the magnification.

In this the voltage V is changed to regulate how much the electron should be accelerated, which in turn changes the wavelength of electron leading to change in magnification.