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Wednesday, October 27, 2010
Ch10 1 #4
See the sheets on intensity, especially sheet 9.2
4 comments:
Anonymous
said...
Dear Professor,
Where is the review material for exam 2? The echo is not posted on blackboard yet.
Hopefully someone can help me in my calculations since I seem to be doing something wrong.
They give L at the the edge of stage, so you can calculate I by doing I=(10^-12)*(10^(110/10))=.1
Then using inverse square law you can get I for where the fan is. (I2/.1)=(1m^2)/31m^2), I2=1.04E-4.
Then using I=P/A, (1.04E-4)=P/pi* (.0042^2), P=5.8E-9. And since they want for 1s, this should be the answer, but apparently I've done something wrong since it's not working. So any help would be appreciated.
You did it correctly, but you have to use the correct distance to the ear of a person. Make a sketch with a person edge of the stage and the position of the speaker. From there I hope it will be clear how you have to scale the intensity to the position of the person.
4 comments:
Dear Professor,
Where is the review material for exam 2? The echo is not posted on blackboard yet.
im having a lot of trouble on this problem. i dont know how to do it
Hopefully someone can help me in my calculations since I seem to be doing something wrong.
They give L at the the edge of stage, so you can calculate I by doing I=(10^-12)*(10^(110/10))=.1
Then using inverse square law you can get I for where the fan is.
(I2/.1)=(1m^2)/31m^2), I2=1.04E-4.
Then using I=P/A, (1.04E-4)=P/pi*
(.0042^2), P=5.8E-9. And since they want for 1s, this should be the answer, but apparently I've done something wrong since it's not working. So any help would be appreciated.
You did it correctly, but you have to use the correct distance to the ear of a person. Make a sketch with a person edge of the stage and the position of the speaker. From there I hope it will be clear how you have to scale the intensity to the position of the person.
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