Does physical interaction with an illusion reveal it to all present?

Question

Many illusion spells contain a statement about physical interaction with the illusion. From Minor Illusion:

... Physical interaction with the image reveals it to be an illusion, because things can pass through it.
If a creature uses its action to examine the sound or image, the creature can determine that it is an illusion with a successful Intelligence (Investigation) check against your spell save DC. If a creature discerns the illusion for what it is, the illusion becomes faint to the creature.

If one creature interacts physically with the illusion, does it become faint only to that creature, or to all who witness the interaction?

Please also address the case of an object not controlled by a creature doing the interaction.

Answer 1

It becomes faint to all who witness the interaction.

Jeremy Crawford, the lead D&D 5e game designer, tweeted the intent behind the rule:

Physical interaction with minor illusion reveals it to be illusory to anyone who witnesses that revelation.

The next paragraph - "if a creature uses its action to examine the sound or image..." - implies examination without physical interaction, which requires a successful Intelligence (Investigation) check and works for a specific creature only (the one who succeeded the check).

Answer 2

It only becomes faint to the creature. According to minor illusions description

. If the creature discerns the illusion for what it is, the illusion becomes faint to the creature.

It implies the fact that a creature has to be the one to interact with the illusion. Assuming touching the illusion or throwing something at the illusion is an act done to discern it as an illusion the only person who should realize what the illusion is should be the one that touched the illusion or threw something at it.

An exception to this would be familiars as a familiar and it's owner share a direct mental link causing the spellcaster to disbelieve the illusion as soon as it's familiar does so.

As for objects that are not thrown by anything such as rain they would not cause someone to disbelieve as it is not an interaction.

Answer 3

This will be situational, depending on who is observing, and how closely. The person who (for example) tosses the torch through the illusion will see it for what it is. Others who clearly witness the torch go through the illusion will also figure it out. Others who are engaged in combat, or other activities, or otherwise occupied/distracted/unable to perceive the event will be unlikely to benefit from the demonstration. DM will have to rule, based on the situation, which characters see through the illusion, which have a chance to (probably by making a saving throw), and which will not have a chance to.