Electron Microscopes
Physics: AQA A Level, topic 12.2.5
Electron Microscopes
Electron microscopes are an alternative to microscopes which use visible light.
Electron microscopes
- Electron microscopes use electrons to scan an object instead of electromagnetic radiation such as light.
- Electron microscopes need to emit electrons with a small de Broglie wavelength to be accurate enough. This requires a potential difference on the anode of at least 150V.
Transmission electron microscope
- A TEM is used for very thin specimens.
- Electrons are projected through the specimen, and the electrons that are able to pass through the specimen form an image.
- Thinner parts of the image will allow more electrons to pass.
Scanning tunneling microscope
- A STM uses a small probe which moves along the sample.
- A potential difference between the sample and the probe allows a current to flow.
- The distance between the probe and the sample will affect the resistance, and hence the current.
- These differences in current can be used to paint an image of the surface on the material.
Test yourself on Electron Microscopes
Transmission Electron Microscope
Which of these statements is true about electron microscopes?