Video Transcript
Which of the following best
explains the difference in resolution between light and electron microscopes? (A) Electron microscopes have a
higher resolution, as they use beams of electrons with short wavelengths. This makes it easier to distinguish
between different structures. (B) Light microscopes have a higher
resolution, as they use waves of light with long wavelengths. This makes it easier to distinguish
between different structures.
To understand how to answer this
question, let’s first review what resolution means. Resolution is the minimum distance
required between two adjacent objects for them to be distinguished as individual
separate objects. It is measured in nanometers. If two objects cannot be resolved,
they will be seen as one object under a microscope.
Light microscopes and electron
microscopes use different sources of illumination. Light microscopes use light, and
electron microscopes use electrons. The wavelength of the illumination
source contributes to the resolution. Here we can see a wave of light
with its wavelength indicated. The wavelength of this light is 400
nanometers, but the wavelength of light can range from 400 to 700 nanometers. On the other hand, electron
microscopes use a beam of electrons. The wavelength of an electron beam
is much shorter than the wavelength of light, at about one nanometer.
One of the factors affecting
resolution is the wavelength of the source of illumination that’s being used. The best light microscopes can
resolve images up to around 200 nanometers apart, which is half of its shortest
wavelength. You can see here that these two
objects are not resolved by light because they’re less than half the wavelength of
light away from each other. On the other hand, the same two
objects placed the same distance from each other with an electron microscope would
be resolved. This is because the wavelength of
an electron beam is much shorter than the distance between the two objects.
Therefore, going back to our
question, the option that best explains the difference in resolution between light
and electron microscopes is given by answer choice (A). Electron microscopes have a higher
resolution, as they use beams of electrons with short wavelengths. This makes it easier to distinguish
between different structures.
