What is the working principle of afm? who can tell me detailed information? any would be appreciated. in advance!

An atomic force microscope is a nano-scale measurement and analysis instrument that touches the surface of a sample to be tested through a micro force-sensitive component (probe). While scanning the surface of the sample, the tiny tip of the force-sensitive component interacts with the surface of the sample. The microcantilever of the force sensitive component is deformed. The laser beam emitted by the laser diode is irradiated on the end of the micro-cantilever of the force-sensitive element. When the micro-cantilever is deformed, the reflected beam of the laser beam also changes correspondingly, and the reflected laser beam is received by the four-quadrant photodetector. The obtained information is converted, amplified, and output a voltage detection signal. The computer adjusts the amount of expansion and contraction of the piezoceramic scanner in the Z-axis direction by comparing the detection signal with a preset reference signal to realize feedback control. The computer processes the detection signal through software programming to obtain the surface topography image of the sample and the corresponding object.

Explanation:

https://www.creative-biostructure.com/Atomic-Force-Microscopy-AFM-Service-653.htm

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.