In imaging and microscopy, what does it mean when a micrograph (for example from an electron microscope) is described as false coloured?

Introduction / Context:

This question deals with interpretation of scientific images, especially those produced by electron microscopes or other instruments that do not naturally capture colour. A micrograph is a photograph or digital image taken through a microscope. Many such images, particularly from scanning electron microscopes, are originally in shades of grey. To make structures easier to see, scientists sometimes apply artificial colours, resulting in a false coloured image.

Given Data / Assumptions:

• The term micrograph includes images from light and electron microscopes.
• Electron microscopes typically capture intensity information, not natural colour.
• The question asks for the meaning of the descriptive phrase false coloured.

Concept / Approach:

False colour imaging means assigning colours to different intensity levels, heights, materials, or other properties in an image that was originally monochrome. The chosen colours are not the actual colours of the sample as seen by the eye. Instead, they are selected to highlight contrasts or specific features so that the viewer can interpret the data more easily. This approach is also used in satellite imagery and medical imaging. True colour images, in contrast, represent colours close to what a human observer would see.

Step-by-Step Solution:

Verification / Alternative check:

Scientific journals often include a note in the figure caption stating that an electron micrograph has been false coloured to highlight specific structures. For example, researchers may colour bacteria in one shade and host cells in another, even though the original image is only grey. Image processing tutorials also explain false colour mapping as a standard technique. These practices confirm that false colour is about artificial colour assignment, not about calibration error or sample glow.

Why Other Options Are Wrong:

• Option B: Incorrect calibration affects measurement accuracy, not whether an image is described as false coloured.
• Option C: Using the wrong optical filter may change the captured colour balance but is not what is meant by false colouring in data visualisation.
• Option D: A sample that emits visible light is described as luminescent, not false coloured, and the colours observed are real emissions.

Common Pitfalls:

Some learners confuse false colour with fake or misleading images. In scientific practice, false colour images are usually clearly labelled and used to communicate data more effectively, not to deceive. Another misunderstanding is to think that any coloured image from an electron microscope must show actual colours of the sample; in reality, nearly all such colours are added later. Remember that false colour is a visualisation tool that maps data values to colours in a deliberate, informative way.

Final Answer:

A false coloured micrograph has colours added artificially to represent features or intensities and does not display the true natural colours of the sample.