AS level MCQ (paper 1) question, help
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AS level MCQ (paper 1) question, help

[From: ] [author: ] [Date: 12-03-11] [Hit: ]
the answer i got doesnt fit any of the options i was given. if an answer was 0.5microseconds, then it wouldve made sense, right?well,......
i don't know from which passpaper it's from but here goes:
A signal has a frequency of 2.0MHz.
What is the period of the signal?
A) 2 microseconds B) 5 microseconds C)200 ns (nanoseconds) D) 500 ns

what i did was:
since frequency = 1 wave/second
i just substituted in 2.0MHz instead of frequency and so: 2.0MHz= 1/s
i then made my "seconds" the subject and so ended up with:
1/2MHz = seconds
1/2MHz= 1/2000000Hz
1/2000000=5x10^-7

and there's when i got stuck. i was like: they didn't teach us the unit for a minus seven?!
also, the answer i got doesn't fit any of the options i was given. if an answer was 0.5microseconds, then it would've made sense, right?

well, it's either something's wrong with the question or my answer. the latter is more likely, so give it a go please and HELP ME!! {:(

-
well, the 5x10^-7 is the right answer. Now you just have to change it into one of the answers given. We know that ns is 10^-9. and your answer is 5x10^-7. Now look at this carefully.
Isn't 5x10^-7 equal to 5 x 10^2 x 10^-9 which is the same as 500 x 10^-9 s.
That makes the answer D) 500ns.
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