Final answer:
Option 3: The photoconductive target in a TV camera's pick-up tube works by changing its conductivity in response to light to generate an electron charge that is converted into a video signal. This process is similar to the photoelectric effect.
Step-by-step explanation:
The photoconductive target in a TV camera's pick-up tube is crucial for converting the light information into an electronic signal that can be processed into a video signal. This target is made of a semiconductive material that changes its electrical conductivity in response to light. When light hits the photoconductive material, it knocks off free electrons, thus creating electron voids. These voids attract nearby electrons, resulting in a chain of electron movement that produces a current.
This current is then used to generate a proportional electron charge at specific positions on the target. Effectively, it creates a voltage potential which is then converted into the video signal that we see on a TV screen. The process is somewhat analogous to the photoelectric effect, where light falling on a metal plate in an evacuated tube ejects electrons that are then collected on a collector wire, measuring a current. In the context of a TV camera, this current is carefully manipulated to accurately represent the intensity of light at different points of the target, which forms the basis of the visual information captured by the camera.