Why do magnets held close to television screens cause the picture to distort?

If you have ever held a magnet near an old television, you likely saw a psychedelic swirl of colors and a warped, melting image. While this looks like a magic trick, it is actually a direct interaction between physics and technology.

However, it is important to distinguish between "old" TVs and modern flat screens, as they react to magnets in completely different ways.

The Secret of the CRT: How Electrons Paint a Picture

To understand why magnets cause distortion, you first have to understand how older televisions—known as Cathode Ray Tubes (CRTs)—work.

Inside a CRT television, there is a vacuum tube with an "electron gun" at the back. This gun fires a constant stream of electrons toward the glass screen, which is coated with light-emitting phosphors. When the electrons hit the phosphors, they glow, creating the image you see.

How Magnets "Bend" the Image

The reason a magnet causes such dramatic distortion on a CRT is that electrons are charged particles. According to the laws of electromagnetism, moving charges are pushed by magnetic fields (a principle known as the Lorentz Force).

Deflection Control: The TV actually uses its own internal electromagnets (called deflection yokes) to steer the electron beam back and forth rapidly to "paint" the picture.

External Interference: When you bring a hand-held magnet close to the screen, its magnetic field overpowers the internal steering system. It pulls or pushes the electron beam off its intended path.

Resulting Distortion: Because the electrons are no longer hitting the correct spots on the screen, the geometry of the image warps. Instead of a square box, you might see a twisted, liquid-looking shape.

Why the Colors Change

On a color CRT, there are three separate electron beams for red, green, and blue. To ensure they hit the right colored phosphors, a thin metal grid called a shadow mask is placed just behind the glass.

Misalignment: When a magnet is nearby, it bends the three beams at different angles. The "red" beam might end up hitting a green or blue phosphor, causing the colors to shift into strange rainbows.

Magnetizing the Mask: A strong magnet can actually "magnetize" the metal shadow mask itself. If this happens, the color distortion remains even after you take the magnet away. This often requires a process called "degaussing" (using a changing magnetic field to neutralize the mask) to fix.

Do Magnets Affect Modern LCD or OLED TVs?

If you try this experiment on a modern LED, LCD, or OLED flat-screen TV, you will notice... nothing happens.

Modern screens operate on entirely different principles:

LCD/LED: These use liquid crystals to block or allow light from a backlight. There are no flying electrons and no internal magnets involved in creating the image.

OLED: These use organic pixels that light up individually when an electric current passes through them.

Because these technologies do not rely on vacuum-sealed electron beams, they are almost entirely immune to household magnets. You can place a powerful neodymium magnet right against an LCD screen without seeing a single swirl of color.

Summary of Magnetic Impact

CRT Televisions: Highly sensitive. Magnets distort the path of electron beams and can permanently discolor the screen by magnetizing the internal metal mask.

LCD/LED/OLED: Not affected. These screens do not use magnetic fields or electron beams to function.

Safety Tip: Even though modern screens aren't distorted by magnets, keep strong magnets away from your computer's Hard Disk Drive (HDD) or credit cards, as these still use magnetic storage that can be erased.