Question

In the context of scanning electron microscopy, match the information in Column I with the most appropriate information in Column II.

• A. P-3; Q-2; R-1; S-4
• B. P-2; Q-4; R-3; S-1
• C. P-1; Q-3; R-2; S-4
• D. P-4; Q-2; R-1; S-3

Hint:

In scanning electron microscopy, secondary electrons are used for topography, backscattered electrons for phase contrast, X-rays for chemical analysis, and diffracted backscattered electrons for crystallography.

Answer 1

The Correct Option is B

In scanning electron microscopy (SEM), various types of electrons are used to gather information about the sample. Let's analyze each type of electron and its application in more detail: P (Secondary Electrons):
Secondary electrons are produced when the primary electrons from the SEM interact with the sample surface and cause the emission of low-energy electrons from the outermost shell of the atoms. These secondary electrons are primarily used to create images of the surface topography of the sample. The secondary electron detector provides high-resolution images of the surface features, which can be used in failure analysis of fractured surfaces. Thus, the correct match for \( P \) is 2. Q (Backscattered Electrons):
Backscattered electrons are high-energy electrons that are reflected back from the sample after interacting with the atoms in the material. The number of backscattered electrons depends on the atomic number of the material. This feature is useful for differentiating between chemically distinct phases in a sample, as heavier elements reflect more backscattered electrons compared to lighter ones. Therefore, backscattered electrons are used for distinguishing chemically distinct phases. Thus, the correct match for \( Q \) is 4. R (Characteristic X-rays):
Characteristic X-rays are emitted when the primary electrons dislodge inner shell electrons from the atoms in the sample, and electrons from higher energy levels fall into the lower energy vacancies, releasing energy in the form of X-rays. These X-rays are characteristic of the elements in the sample and can be used for chemical composition analysis of the material. Therefore, the correct match for \( R \) is 3. S (Diffracted Backscattered Electrons):
Diffracted backscattered electrons are electrons that are diffracted due to the crystalline structure of the material. The angle of diffraction can provide information about the crystallographic orientation of grains in the material. Thus, diffracted backscattered electrons are used for crystallographic orientation of grains. The correct match for \( S \) is 1. Final Answer: \text{(B) P-2; Q-4; R-3; S-1}