The grains that appear on a television set when operated are also referred to as

Concept: A television receiver amplifies whatever reaches its input. Every amplifier stage also generates its own random thermal noise, and the antenna adds random atmospheric noise. When no carrier is present, or the carrier is too weak to dominate, it is this random noise that gets amplified and painted onto the screen.

Application: Random noise carries no picture information, so the brightness of each point on the screen is fixed by an unrelated random value, and a fresh set of values is drawn for every frame. What the viewer sees is a dense field of light and dark specks flickering many times a second, with a hiss in the audio. Broadcast and television-service literature names this speckled pattern snow (also called static or noise), by analogy with falling snowflakes. That is the term the question is asking for.

Contrast with the other terms:

• sparks — brief luminous discharges that jump an air gap once the electric field there exceeds the dielectric strength of air; a high-voltage wiring phenomenon, not a picture pattern.

• green dots — the green-emitting phosphor elements of a colour picture tube, one of the three primary-colour elements in every red-green-blue triad; a construction feature of the screen rather than a noise pattern.

• rain drops — water droplets; in television usage the phrase describes droplets on the screen surface or precipitation inside the pictured scene, not receiver noise.

Cross-check: The same effect is what appears on an unused analogue channel, and the accompanying audio is called static or hiss — the standard service-manual pairing "snow and static" confirms that snow is the name of the visual speckle.