Automatic doors use a beam of light that shines continuously on a Photo-detector

Question

Automatic doors use a beam of light that shines continuously on a Photo-detector. The door will open when a person approaches the door and blocks the beam of light. Which phenomenon explains why the door will open when the beam of light is blocked? Compton scattering Diffraction Interference Photoelectric effect Students were working in a lab using spectroscopes to look at different gas-discharge tubes. While looking through the tubes, they noticed that the diffraction grating produced a series of white lines known as refractors. white lines known as the visible line spectrum. colored lines known as refractors. colored lines known as the visible line spectrum.

Explanation / Answer

1. (D) is the correct option i.e. photo electric effect .

2. (B) is correct option

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