Exercises: Cell observation

Distinguish between light microscopy and electron microscopy: what each uses to "illuminate" the sample, what type of structures each technique allows us to observe, and whether it is possible to observe living cells with them.

The diagram shows a scale of sizes with the resolution limits of the human eye, the light microscope (LM) and the transmission electron microscope (TEM). State which instrument you would need to observe in detail: a) a flu virus; b) a bacterium; c) a ribosome; d) a skin cell. Justify each choice based on the diagram.

Explain the difference between magnification and resolving power of a microscope and explain why greatly magnifying an image without improving resolution (so-called "empty magnification") does not allow further details to be distinguished.

The electron microscope reveals organelles and viruses that the light microscope cannot show. Explain which property of the electron beam gives it a higher resolving power and point out two practical limitations of electron microscopy compared to light microscopy.