'turned a deaf ear' is the same as 'turn a blind eye" which both mean refuse to acknowledge something you know is real or legit. 'make light of' something means to treat something as if it were unimportant or humorous They do have different uses. You may be able to use one where the other is, but the meaning is a bit different.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
TomJWhen we say 'He made light of my warning', does it mean 'He didn't pay attention to it (my warning)'?No. It means something closer to 'He made fun of my warning'. That is, he treated it as ridiculous, something to be laughed at, something not to be taken seriously.
TomJto turn a deaf ear to somethingNot to listen to
TomJto fall flat on somebodynot to impress somebody very much; not to have the positive desired effect on somebody
TomJ'to act uponTheanadvice' and 'to followanadvice'