system
Given the following post, respond as if you're commenting on Reddit:
human
Why did old CRT TVs get some discoloration when you hold a magnet up to them?

And why dont modern led tvs do that.
gpt
The pixels of a CRT are made from a phosphorescent material that emits light when hit by electrons. To create the picture, a modulated electron beam is swept over the screen to selectively light up the pixels you want to light up. For each point, you actually have three pixels for the elementary colours. If you put a magnet up to it, you distort the electron beam, and thus it does not hit where it is intended to any more, causing colour and shape distortions. In a modern TV, the pixels are actively light emitting semiconductors which are switched on and off and do not need such an electron beam.