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Kecepatan elektron yang keluar dari suatu logam ketika diberi cahaya berfrekuensi 1,5×1015 Hz adalah 6×105 m/s. Berapakah kecepatan elektron yang keluar jika logam disinari cahaya yang berfrekuensi 2×1015 Hz?

Pertanyaan

Kecepatan elektron yang keluar dari suatu logam ketika diberi cahaya berfrekuensi begin mathsize 14px style 1 comma 5 cross times 10 to the power of 15 space Hz end style adalah begin mathsize 14px style 6 cross times 10 to the power of 5 space straight m divided by straight s end style. Berapakah kecepatan elektron yang keluar jika logam disinari cahaya yang berfrekuensi begin mathsize 14px style 2 cross times 10 to the power of 15 space Hz end style?

R. Anjasmara

Master Teacher

Mahasiswa/Alumni Universitas Riau

Jawaban terverifikasi

Jawaban

kecepatan elektron yang keluar dari logam adalah begin mathsize 14px style 1 comma 043 cross times 10 to the power of 6 space straight m divided by straight s end style.

Pembahasan

Soal ini dapat dikerjakan menggunakan persamaan efek fotolistrik.

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell E K end cell equals cell E minus E subscript 0 end cell row cell 1 half m subscript e v squared end cell equals cell h open parentheses f minus f subscript 0 close parentheses end cell row cell f subscript 0 end cell equals cell f minus fraction numerator 1 half m subscript e v squared over denominator h end fraction end cell row blank equals cell 1 comma 5 cross times 10 to the power of 15 minus fraction numerator begin display style 1 half end style cross times 9 comma 1 cross times 10 to the power of negative 31 end exponent cross times open parentheses 6 cross times 10 to the power of 5 close parentheses squared over denominator 6 comma 625 cross times 10 to the power of negative 34 end exponent end fraction end cell row blank equals cell 1 comma 5 cross times 10 to the power of 15 minus fraction numerator begin display style 163 comma 8 cross times 10 to the power of negative 21 end exponent end style over denominator 6 comma 625 cross times 10 to the power of negative 34 end exponent end fraction end cell row blank equals cell 1 comma 5 cross times 10 to the power of 15 minus 0 comma 25 cross times 10 to the power of 15 end cell row blank equals cell 1 comma 25 cross times 10 to the power of 15 space Hz end cell end table end style 

Karena memakai logam yang sama maka;

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell E K end cell equals cell E minus E subscript 0 end cell row cell 1 half m subscript e v squared end cell equals cell h left parenthesis f minus f subscript 0 right parenthesis end cell row cell v squared end cell equals cell fraction numerator h left parenthesis f minus f subscript 0 right parenthesis over denominator 1 half m subscript e end fraction end cell row cell v squared end cell equals cell fraction numerator 6 comma 625 cross times 10 to the power of negative 34 end exponent left parenthesis 2 cross times 10 to the power of 15 minus 1 comma 25 cross times 10 to the power of 15 right parenthesis over denominator 1 half cross times 9 comma 1 cross times 10 to the power of negative 31 end exponent end fraction end cell row blank equals cell fraction numerator 4 comma 968 cross times 10 to the power of negative 19 end exponent over denominator 4 comma 55 cross times 10 to the power of negative 31 end exponent end fraction end cell row v equals cell square root of 1 comma 0918 cross times 10 to the power of 12 end root end cell row blank equals cell 1 comma 043 cross times 10 to the power of 6 space straight m divided by straight s end cell end table end style 

Dengan demikian, kecepatan elektron yang keluar dari logam adalah begin mathsize 14px style 1 comma 043 cross times 10 to the power of 6 space straight m divided by straight s end style.

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