why a strong magnet held near a CRT tv cause the picure become distorted?

Answer 1

The electron gun in a CRT shoots a beam of electrons at the screen, the electrons strike the phosphors on the screen, causing them to glow. There is only one beam (okay, three -- one for each color), and the CRT has electromagnets to deflect the beam along both X and Y axes, to scan the whole screen. So when you put a strong enough magnet close to the screen, you deflect the beam to where it shouldn't be, distorting the image.
In your CRT, there is an device called an aperture grille (or a shadow mask in older designs) that ensures the beam only strikes the right color phosphors. When you bend the beam, this can't work properly, so you end up with strange color effects too.
I recently did this with a pretty strong magnet, and the effects stayed even after I removed the magnet! I had to degauss the monitor to get it back to normal.

Answer 2

The CRT tv works by shooting electrons at the screen pixel by pixel which creates the image. When you place a maget near the TV, the path of the electrons gets distorted and they no longer hit the screen at the locations they were intended to hit, hence the distortion

Answer 3

A CRT shoots a beam of electrons against a phosphor screen.

When you add the strong magnetic field, it distorts where the electrons are hitting (electrons = negative charge); since they are not hitting where they should, the screen gets all funky.

Answer 4

the distortion that occurs is via the illustration of magnetic field strains of the magnet. the unfastened electrons are then held in this sort of way that they sort the direction of the strains.