intensity relationship to frequency?

[medscholhopeful]

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I am reading EK physic and they say the intensity is proportional to the square of the amplitude and and frequency... I get the why it is proportional to the amplitude(cos that has to do with the energy of the wave) but i can't seem to understand what the frequency gotta do with it???

also #128 in the same book says
If the intensity of a sound is doubled, the decibel level will increase by
A less than 10dB (correct ans)
B exactly 1db( i chose this bad boy..but it was wrong!!)
C more than 10dB
D exactly 20dB

my logic.. if the intensity is double which will be equal to 100, then the decibel level should be increased by 10dB right??

 

[medscholhopeful]

bump.. i know someone has a inkling..pleaseee..

 

[thebillsfan]

no. decibel is on a log scale. doubling the intensity only increases it by 3 i believe. increasing it by ten will add ten to the decibel scale. the point is that a doubling of the intensity doesnt double the number of decibels

 

[medscholhopeful]

no. decibel is on a log scale. doubling the intensity only increases it by 3 i believe. increasing it by ten will add ten to the decibel scale. the point is that a doubling of the intensity doesnt double the number of decibels

hmmn so why did EK say in the book when intensity increases by a factor of 10, the decibels increase by the addition of 10. In other words an increase in intensity from 30W/meters square to 3000W/meers square is equivalent to an increase in 20decibels.(this is straight form the book)... i'm confused

 

[unDRdog]

Heres the deal; If the intensity increases by a factor of 10, then the intensity level increases by 10dB. So... if something increases say 30db you can see the the intensity increases by a factor of 1000. (10 x 10 x 10 )--- hope this helps.

 

[inaccensa]

I am reading EK physic and they say the intensity is proportional to the square of the amplitude and and frequency... I get the why it is proportional to the amplitude(cos that has to do with the energy of the wave) but i can't seem to understand what the frequency gotta do with it???

also #128 in the same book says
If the intensity of a sound is doubled, the decibel level will increase by
A less than 10dB (correct ans)
B exactly 1db( i chose this bad boy..but it was wrong!!)
C more than 10dB
D exactly 20dB

my logic.. if the intensity is double which will be equal to 100, then the decibel level should be increased by 10dB right??

I think they are asking you if it is "doubled" So, if the intensity was lets say 4, then doubling it will give you 16. Even if initial intensity was 10, doubling that will give you 20 and not 100.

 

[ratatat]

Yeah think of it is like this:

10db = 10^1 change..ie. 10 times
20 db = 10^2 change ie. 100 times
30 db = 10^3 change ie. 1000 times

So let's say the digit in the tens column is x. The change in the intensity is 10^x.

 

[unDRdog]

Yeah think of it is like this:

10db = 10^1 change..ie. 10 times
20 db = 10^2 change ie. 100 times
30 db = 10^3 change ie. 1000 times

So let's say the digit in the tens column is x. The change in the intensity is 10^x.

Correction to my earlier post: 1000 not 10,000..sorry for the typo

 

[inaccensa]

I think they are asking you if it is "doubled" So, if the intensity was lets say 4, then doubling it will give you 16. Even if initial intensity was 10, doubling that will give you 20 and not 100.

oops sorry, if u double 4, u get 8, not 16!!

 

[SFs Own Tone]

I am reading EK physic and they say the intensity is proportional to the square of the amplitude and and frequency... I get the why it is proportional to the amplitude(cos that has to do with the energy of the wave) but i can't seem to understand what the frequency gotta do with it???

also #128 in the same book says
If the intensity of a sound is doubled, the decibel level will increase by
A less than 10dB (correct ans)
B exactly 1db( i chose this bad boy..but it was wrong!!)
C more than 10dB
D exactly 20dB

my logic.. if the intensity is double which will be equal to 100, then the decibel level should be increased by 10dB right??

Everyone is answering your decibel problem so I'm gonna answer your frequency problem.

Imagine if one wave were a slap in the face. If i told you I was gonna slap you once a day. Your face wouldn't hurt that much.
If i told you I was gonna slap you every 5 minutes. Your face would hurt a lot. and probably so would my hand.
Amplitude would be how hard I slapped you. Frequency would be how often.