Final answer:
The main difference between TEM and SEM is that TEM images the interior of a specimen at high magnification and requires thin sections, while SEM scans the surface to provide detailed, three-dimensional images at a slightly lower resolution and without the need for extremely thin samples.
Step-by-step explanation:
Main Difference Between TEM and SEM
The main difference between a transmission electron micrograph (TEM) and a scanning electron micrograph (SEM) is how they interact with the specimen to create an image. TEM works by transmitting a beam of electrons through a specimen and capturing the image based on electrons that pass through, it thus requires the sample to be very thin. It allows for high magnification up to two million times and is used to view internal structures at high resolution. On the other hand, SEM slides a beam of electrons across the surface of a specimen, detecting secondary electrons that are emitted. This produces a highly detailed image with a three-dimensional appearance but at a lower resolution. SEM does not require the sample to be as thin as for TEM, and it can magnify up to 500,000 times.
Specimen preparation for the two also differs; SEM involves sputter-coating the sample with a conductive material, typically metal, while TEM requires the specimen to be cut into very thin sections for electron transparency.