Macmillan Dictionary gave the following rules that will help us learn how to use ‘look at and look on.

a. Look on
1. look on someone/something– to think of someone or something in a particular way.
Ex. I look on it as a challenge.
2. look on someone/something– to watch an activity or event without taking part in it
Ex. Phil looked on in disbelief as Maggie got up on the table and started to dance.
b. Look at
1. look at someone/something– to direct your eyes toward someone or something so that you can see them
Ex. He turned and looked at her.
2. look at something– to think about a situation or subject carefully,especially in order to make a decision
Ex. We’re looking carefully at all the options.
3. look at something– to read something quickly so that you can give an opinion on it
Ex. Would you like me to look at your essay before you hand it in?
4. look at someone/something– if an expert looks at someone or something, they examine them and decide what to do
Ex. I’d like a skin specialist to look at that rash of yours.
To read more about ‘look at’, please click here and here.
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