Radiologic Technologist Practice Exam

When do charges separate in amorphous silicon?

1. When light interacts with the array

2. When the CCD activates the array

3. When an electric field is applied to the array

4. When the capacitor is activated

The correct answer is: When an electric field is applied to the array

The correct answer highlights the importance of the electric field in the functioning of amorphous silicon. In amorphous silicon, the separation of charges occurs when an electric field is applied to the material. This electric field causes the positive and negative charges generated by the absorption of photons (light energy) to move in opposite directions, effectively creating a flow of charge carriers. This process is crucial for the operation of devices like photodiodes and solar cells, where the conversion of light energy into electrical energy relies on the efficient separation of these charges. The other options touch on relevant concepts but do not directly lead to the separation of charges. For instance, while light interacting with the array can generate electron-hole pairs, without an electric field, these charges would not separate and would instead recombine. Similarly, while a CCD (charge-coupled device) may relate to the processing of image data, it does not specifically cause charge separation in the amorphous silicon itself. Lastly, activating the capacitor is part of the overall circuitry that may help in charge collection, but it does not initiate the fundamental charge separation process that occurs due to the influence of the electric field.