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Jika cahaya dengan panjang gelombang 4.500 Å jatuh...

Jika cahaya dengan panjang gelombang 4.500 Å jatuh pada sebuah permukaan, didapatkan bahwa potensial henti elektron-elektron yang dipancarkan ini 0,75 V. Berapakah potensial henti elektron foto jika cahaya dengan panjang gelombang 3.000 Å jatuh pada permukaan tersebut?undefined 

Jawaban:

begin mathsize 14px style lambda subscript 1 equals 4.500 space straight Å equals 4 comma 5 cross times 10 to the power of negative 7 end exponent space straight m V subscript s 1 end subscript equals 0 comma 75 space straight V lambda subscript 2 equals 3.000 space straight Å equals 3 cross times 10 to the power of negative 7 end exponent space straight m end style 

Ditanyakan: begin mathsize 14px style V subscript s 2 end subscript equals ? end style 
Jawab:

begin mathsize 14px style E k equals q. V subscript s 1 end subscript E k subscript 1 equals open parentheses 1 comma 6 cross times 10 to the power of negative 19 end exponent close parentheses open parentheses 0 comma 75 close parentheses E k subscript 1 equals 1 comma 2 cross times 10 to the power of negative 19 end exponent space straight J end style 

Maka fungsi kerja logam
begin mathsize 14px style E k subscript 1 equals h c over lambda minus W subscript 0 1 comma 2 cross times 10 to the power of negative 19 end exponent equals open parentheses 6 comma 63 cross times 10 to the power of negative 34 end exponent close parentheses fraction numerator open parentheses 3 cross times 10 to the power of 8 close parentheses over denominator open parentheses 4 comma 5 cross times 10 to the power of negative 7 end exponent close parentheses end fraction minus W subscript 0 1 comma 2 cross times 10 to the power of negative 19 end exponent equals 4 comma 42 cross times 10 to the power of negative 19 end exponent minus W subscript 0 W subscript 0 equals 3 comma 22 cross times 10 to the power of negative 19 end exponent space straight J end style  

Sehingga potensial henti untuk panjang gelombang kedua
begin mathsize 14px style V subscript s 2 end subscript equals fraction numerator E k subscript 2 over denominator q end fraction V subscript s 2 end subscript equals fraction numerator E subscript 2 minus W subscript 0 over denominator q end fraction V subscript s 2 end subscript equals fraction numerator h begin display style c over lambda subscript 2 end style minus W subscript 0 over denominator q end fraction V subscript s 2 end subscript equals fraction numerator open parentheses 6 comma 63 cross times 10 to the power of negative 34 end exponent close parentheses begin display style fraction numerator open parentheses 3 cross times 10 to the power of 8 close parentheses over denominator open parentheses 3 cross times 10 to the power of negative 7 end exponent close parentheses end fraction end style minus open parentheses 3 comma 22 cross times 10 to the power of negative 19 end exponent close parentheses over denominator 1 comma 6 cross times 10 to the power of negative 19 end exponent end fraction V subscript s 2 end subscript equals fraction numerator 3 comma 41 cross times 10 to the power of negative 19 end exponent over denominator 1 comma 6 cross times 10 to the power of negative 19 end exponent end fraction V subscript s 2 end subscript equals 2 comma 13 space straight V end style 

Jadi, potensial henti ketika panjang gelombang 3.000 Å adalah 2,13 V.

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