In electron microscopy, dark areas appear on the image due to which cause?

• A. Deflected electrons
• B. Absorbed light
• C. Specular reflection
• D. Thermal noise

Answer: (A)

In electron microscopy, image contrast comes from how the specimen interacts with the incoming electron beam. The number of electrons that reach the detector from a given spot determines how bright that spot appears. When the sample causes electrons to be deflected away from the detector (or absorbed by the sample), fewer electrons are collected from that area, so it looks dark. This is the primary reason dark regions appear.

Light-based ideas aren’t applicable here, since photons aren’t involved in forming the image, and specular reflection isn’t the mechanism used in EM imaging. Thermal noise can affect overall image quality but doesn’t create the characteristic dark areas tied to the sample’s interaction with the electron beam.