I find it hard to believe it means "It is due to the light", as they corrected me.
Which sentence are you talking about? If the sentence was "Es ist wegen des Lichts", the English translation is correct.
Sorry, I see the post is not complete. The sentence was "Es liegt im Licht".
Yes, I'm sure I'm right. German is my native language :). "liegen an + dative" can have a literal meaning, e.g. "Sie liegt am Strand" (She is lying on the beach). However, "liegen an + dative" can also have another meaning: "to be due to sth./to be caused by sth."
You can see what I mean when you type in "liegen" in the search box of this online dictionary and have a look at meaning 18.
Then Duolingo is wrong: "Es liegt AM Licht" means "It is due to the light". "Es liegt IM Licht" means "It lies/It is lying in the light". It's probably a typo in the programme.
Maybe it was "Es liegt AM Licht". But are you sure it means "It is due to the light"? I seriously doubt it. If you are sure it's right, please explain. Thanks :)
Do you have a problem with the English sentence, or the German one? "It is due to the light" might be a little uncommon, but it's certainly valid as a sentence... The photograph faded. It is due to the light. The grass grew. It is due to the light.