This is the 113th most frequent French word.
effet
Effect.
Here, 'effet' is used to mean 'effect,' describing the result or consequence of light impacting the painting.
L'effet de la lumière sur ce tableau est magnifique.
The effect of the light on this painting is magnificent.
In this case, 'effet' is part of the expression 'en effet,' which means 'indeed' or 'in fact,' to confirm or elaborate on a previous statement.
En effet, il a raison de dire cela.
Indeed, he is right to say that.
Here, 'effet' refers to being under the influence or impact of an external factor, often implying an observable change in behavior or state.