Imagine a situation: my son is going to have his dinner and I want to know if his hands are clean.
Which of the following questions are correct ?
a) Did you wash your hands after you came home ?
b) Have you washed your hands after you came home ?
c) Had you washed your hands after you came home ?
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(a) Did you wash your hands after you came home ?
(b) Have you washed your hands after you came home ?
(c) Had you washed your hands after you came home ?
(a) is ok, (b) and (c) are wrong.
I think the sentence really should be "Have you washed your hands since you came home?"
(a) The phrase "Did you wash your hands" is asking about an action in the past tense, so the hand washing should have already have taken place. The whole sentence construction is common.
Had in (c) is past tense. Since you are talking to your son in the present that is the wrong tense.
The after/since is a bit trickery to explain. After means did your son ever wash his hands after coming home sometime (but he should know what you mean...). Since restricts the time period to between when he came home and the time you asked the question (now). If you really really want to nail it down...
"Have you washed your hands since you came home today?"
If he has been in and out of the house three times since getting home from school...
"Have you washed your hands since the last time you came inside?"
(a) and (c) Would be like your son is at his grandmothers whining about you fussing at him yesterday. So grandmother asks "Did you wash your hands after you came home?" or "Had you washed your hands after you came home ?"
a) is correct. The pattern of that sentence is
[clause in simple past tense] ["after" clause in simple past tense]
This pattern is really really common in English.
b) is incorrect. The pattern of that sentence is
[clause in present perfect tense] ["after" clause in simple past tense]
This pattern is never used.
A present perfect tense clause is not used with an "after" clause. An "after" clause tells you a specific event occurs at a later time. Whenever you have the pattern
[clause a] after [clause b]
[clause a] should be a description of a specific event like "John ate an apple". The present perfect tense is not describing a specific event, it is merely a statement saying that an event existed. It's a subtle difference, but basically:
A simple past tense clause is a concrete action. If someone said,
Please draw a picture of "John ate an apple"
you would draw a picture of a man eating an apple, because the sentence is a concrete description. But if someone asked you
Please draw a picture of "John has eaten an apple (in his lifetime)"
you would draw nothing, because the sentence is just an abstract fact.
On the other hand, you could use the pattern
[clause in present perfect tense] ["since" clause in simple past tense]
Because the word "since" is used with non-specific events. It makes sense, because "since B" tells you about the all the moments after B. Whereas "after B" tell you about a specific moment after B.
So you could ask
Have you washed your hands since you came home?
c) Wrong for the same reasons as b)
