A Level Biology Practice Exam

What does scanning electron microscopy produce?

1. A two-dimensional image of internal cell structures

2. A three-dimensional image of the specimen surface

3. A series of light-based images of living cells

4. A chemical analysis of specimen elements

The correct answer is: A three-dimensional image of the specimen surface

Scanning electron microscopy (SEM) is a powerful imaging technique used to obtain detailed images of the surfaces of specimens. It functions by scanning a focused beam of electrons across the surface of the sample, which causes secondary electrons to be emitted. These emitted electrons are then collected to form an image that reflects the surface topography. The result is a three-dimensional representation of the specimen's surface, revealing intricate details that would not be visible with light microscopy. This technique is particularly useful for examining the morphology of cells, tissues, and materials at a high resolution. The three-dimensional quality of the images produced by SEM allows researchers to analyze the structure and contours in depth, providing insights into the surface features and textures. In contrast, the options suggesting a two-dimensional image of internal structures or light-based images of living cells do not accurately capture the nature of SEM. Furthermore, while chemical analysis can be conducted using techniques complementary to SEM, the primary output of scanning electron microscopy itself is not a chemical analysis but rather high-resolution surface images.