# DBT JRF 2020 — Question 12

Exam: DBT JRF 2020 · Section: B · Topic: Biotechnology · Difficulty: Medium

## Question

In Transmission Electron Microscope (TEM), a beam of electrons interact with the specimen to form image as

## Options

- **A.** diffraction
- **B.** reflection
- **C.** scattering
- **D.** shadow

## Answer

Option A

## Explanation

In TEM, a focused beam of high-energy electrons (typically 60–300 keV) is transmitted through an ultra-thin specimen (50–100 nm). Electrons interact with the specimen: areas of high electron density (heavy metal stains, dense organelles) scatter electrons strongly and appear DARK; electron-lucent areas transmit more electrons and appear LIGHT. The transmitted electron beam is focused by electromagnetic lenses onto a fluorescent screen or CCD detector. The image is essentially a two-dimensional shadow/projection of the specimen's density variations. This is different from SEM (which uses reflected/secondary electrons to give surface topology images) and different from diffraction patterns.

Source: https://mypyqbuddy.com/questions/in-transmission-electron-microscope-tem-a-beam-of-6a05a8a02adafec470293224