First, you need to drop the 'the'. Sentence should read, "I wonder if age will deepen the lines in my face when I am 40" One of the usages of 'will' is making predictions about the future. Here, the speaker is making a prediction (using 'will') that the lines in their face are going to deepen when they are 40. Another example of making a prediction using 'will' is, "She will be sick if she keeps eating too much".

Not every sentence with "if" is a conditional sentence. If "if" can be replaced with "whether," you can use it with indicative mood, and normal tenses. past: I wonder if/whether he went there yesterday. present: I wonder if/whether he is happy today. present perfect: I wonder if/whether he has ever gone there. future: I wonder if/whether he will go there next year.

In agreement with what has already been said, I would just add: remember that Type 1 Conditional sentences take the simple present, using 'will' or whatever verb it happens to be. In Type 1 Conditional sentences, you do not use 'would'.

The sentence isn't correct. You need to use 'would' instead of 'will'. I wonder if 'my' age 'would' deepen the lines in my face when I am 40.