usage of 'as' and 'when'
Hi.
I learned that 'as' can be used to describe that two things happened at the same time, or something happened in the middle of doing something, or two things happened together in a longer period of time.
Also, when is similar to as, as in the meaning of when means something happened at the same time.

These are sentences related to as and when
1) He dropped the glass (as/when) he was taking it out of the cabinet
The answer is as. I agree with it but I also think that when is possible. Does 'when' can be an answer without changing the meaning?

2) My camera was stolen (as/when) I was asleep on the beach
The answer is when, but I don't understand why 'as' can't be an answer. Is it because if I want to use 'as' for that something happened in the middle of doing something, then the subordinate clause should be progressive?

3) The train slowed down (as/when) it approached the station
The answer is as. The reason why 'when' cannot be an answer is that when 'when' is used in the meaning of that something happened at the same time, two things should happen in a short amount of time?

Thank you.

Question

usage of 'as' and 'when'
Hi. 
I learned that 'as' can be used to describe that two things happened at the same time, or something happened in the middle of doing something, or two things happened together in a longer period of time.
Also, when is similar to as, as in the meaning of when means something happened at the same time.

These are sentences related to as and when
1) He dropped the glass (as/when) he was taking it out of the cabinet
The answer is as. I agree with it but I also think that when is possible. Does 'when' can be an answer without changing the meaning?

2) My camera was stolen (as/when) I was asleep on the beach
The answer is when, but I don't understand why 'as' can't be an answer. Is it because if I want to use 'as' for that something happened in the middle of doing something, then the subordinate clause should be progressive?

3) The train slowed down (as/when) it approached the station
The answer is as. The reason why 'when' cannot be an answer is that when 'when' is used in the meaning of that something happened at the same time, two things should happen in a short amount of time?

Thank you.

Answer

I can't give you a technical answer :) 
I will give you an answer from a colloquial perspective, not a formal or test-taking perspective.

In either of those 3 cases, you could use either "as" or "when". I generally hear "when" used more than "as". "As" sounds a bit more formal. However, I do agree with the official answer given for each question.

In conclusion, on a test, the answers you were given to the questions are right. However, in everyday use, either answer is okay for all three questions :)

For #2, yes, "My camera was stolen as I was sleeping on the beach." would be technically correct (using the progressive). But again, in everyday language, you could also say "when".

For #3, from a technical/more formal perspective, using when sounds like...it's too late? If you did it "when" you approached the station it would be too late to stop. "as it approached" or "as it was approaching" makes more sense. But again, in casual language, either is okay.

For #1, yes, using "when" would not change the meaning. The "correct" answer is "as" because it is "taking" and the breaking occurred in the middle of the action, but really either word is okay in everyday language.

Sorry my answers are not very technical for exam purposes, but I hope it will help you with your colloquial speaking and writing :)

Just remember that English is a very complex and confusing language and there are a lot of rules that native speakers will regularly break as a part of natural speaking and writing :)