Logarithms, Explained - Steve Kelly

1,844,528 views ・ 2012-08-20

TED-Ed


Please double-click on the English subtitles below to play the video.

Translator: Hekim Atay Reviewer: Mehmet Sıddık Dilek
00:15
How does the difference between
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Cudatiya navbera 0, 0000000398 û
00:17
point 0000000398 and
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00:20
point 00000000398
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0,00000000398'ê çawa dibe sedema
00:25
cause one to have red eyes after swimming?
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çavsoriya piştê avjeniyê?
00:27
To answer this, we first need a way of
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Ji bo bersiva vê,
00:29
dealing with rather small numbers,
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ji bo ceribandina hejmarên piçûk û mezin
00:32
or in some cases extremely large numbers.
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rêyek hewce ye.
00:34
This leads us to the concept of logarithms.
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Ev jî têgeha Logarîtmayê tîne bîra me.
00:36
Well, what are logarithms?
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Logarîtma çi ye?
00:37
Let's take the base number, b,
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Hejmara bingeh b
00:40
and raise it to a power, p,
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ya li ser "p"yê hildin.
00:41
like 2 to the 3rd power,
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wek mînak 3 li ser 2yê
00:43
and have it equal a number n.
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Ev jî yeksanê "n"yê be.
00:45
We get an exponential equation: b raised to the p power, equals n.
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yeksaniyek heye: ser b yê p yeksan n ye.
00:49
In our example, that'd be 2 raised
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di mînakê de, ev 3 li ser 2yê ye,
00:51
to the 3rd power, equals 8.
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yeksanê 8ê ye.
00:53
The exponent p is said to be
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"p"ya ku hejmara ser e,
00:55
the logarithm of the number n.
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logarîtmaya "n"yê ye.
00:57
Most of the time this would be written:
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Ev wiha jî tê nivîsîn "Logarîtma li bin b
00:59
"log, base b, of a number equals p, the power."
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yeksanê "p"ya li ser e."
01:03
This is starting to sound a bit confusing with all the variables,
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Mesele hinekî tevlihev dibe,
01:06
so let's show this with an example.
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Lewma em mînakekê bidin
01:08
What is the value of
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Bin log 10 nirxa 10.000'î çi ye?
01:09
log base 10 of 10,000?
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01:11
The same question could be asked using exponents:
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Wiha jî dikarî bipirsî:
01:14
"10 raised to what power is 10,000?"
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Li ser 10î çend, dike 10.000?
01:16
Well, 10 to the 4th is 10,000.
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Li ser 10î 4 dike 10.000
01:18
So, log base 10 of 10,000
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Ango, bingeha 10ê log 10.000
01:20
must equal 4.
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yeksanê 4an e.
01:22
This example can also be completed very simply on a scientific calculator.
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Ev hesab bi makînê, bi hesanî tê hesabkirin
01:26
Log base 10 is used so frequently
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Logarîtmayên bingeh 10,
01:28
in the sciences
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di zanistîyê de hingî tê bikaranîn
01:29
that it has the honor of having its own button on most calculators.
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di gelek makînayan de cihê wê taybet e.
01:34
If the calculator will figure out logs for me,
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Mafir makîneyên bersê vê hesab dikin,
01:37
why study them?
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em çima mijul dibin? niha bibêjim;
01:38
Just a quick reminder:
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01:39
the log button only computes logarithms of base 10.
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Tûşa log tenê bi bingeha 10î hesab dike.
01:43
What if you want to go into computer science
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Hûn bi zanistiya computerê re têkildar bin
01:45
and need to understand base 2?
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û bingeha 2yê hewce be?
01:47
So what is log base 2 of 64?
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Log 64 bi bingeha 2yan çi ye?
01:50
In other words, 2 raised to what power is 64?
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Ango, li ser 2yan çend, 64 e?
01:53
Well, use your fingers. 2, 4, 8, 16, 32, 64.
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Bi tiliyan bijmirin, 2, 4, 8, 16, 32, 64.
Ango bi bingeha 2yan, log 64 yeksanê 6ê ye
01:59
So log base 2 of 64 must equal 6.
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02:03
So what does this have to do with my eyes turning red
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Çima çavê me hinan sor dibin, hinan nabin?
02:06
in some swimming pools
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Çi têkiliya vê heye?
02:07
and not others?
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02:08
Well, it leads us into an interesting
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Li vir, têkiliyeke ecêb ya
02:10
use of logarithms in chemistry:
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logarîtma û kîmyayê heye.
02:12
finding the pH of water samples.
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dîtina pH'ê
pH asîdtî û bazîkiyê eşkere dike.
02:14
pH tells us how acidic or basic a sample is,
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02:17
and can be calculated with the formula:
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Formûl;
02:19
pH equals negative log base 10 of the hydrogen ion concentration, or H plus.
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pH= -log10 [+H]
02:25
We can find the pH of water samples
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pH'a Avên tîrîtiya hîdrojenê 0, 0000000398
02:27
with hydrogen ion concentration of point 0000000398
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û 00000000398
02:33
and point 00000000398
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bi makînê bibînin.
02:38
quickly on a calculator.
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02:39
Punch: negative log of each of those numbers,
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Dûre -logarîtmaya wan hildin.
02:41
and you'll see the pH's are 7.4 and 8.4.
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pH 7,4 û 8,4 dertê.
02:46
Since the tears in our eyes have a pH of about 7.4,
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pH'a hêsirê 7,4 e
02:49
the H plus concentration of .0000000398
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0,70398 H
02:53
will feel nice on your eyes,
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ji çavan re baş tê,
02:54
but the pH of 8.4 will make you feel itchy and red.
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8,4 pH çavan sor dike û dixurîne.
"logarîtmaya "n"ya bi bingeha "b"yê yeksanê "p"yê ye.
02:59
It's easy to remember logarithms "log base b of some number n equals p"
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03:04
by repeating: "The base raised to what power equals the number?"
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dubare bikin: "li ser çendan yeksanê wê ye?"
03:07
"The BASE raised to what POWER equals the NUMBER?"
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"Li ser(p) çendan (b) yeksanê wê(n) ye.
03:12
So now we know logarithms are very powerful
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Êdî em dizanin, Logarîtma
03:14
when dealing with extremely small or large numbers.
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ji bo hesabkirina hejmarê pir biçûk û mezin gelek bi kêr tê.
Hetta ku, hûn dikarin logarîtmayê
03:18
Logarithms can even be used
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03:19
instead of eyedrops after swimming.
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piştê avjeniyê wek derman bikarînin.
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