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← JEE Main 2022 · 29 Jun · Shift 2
PhysicsInteger+4 / -1Question 55 of 90

JEE Main 2022 · 29 Jun · Shift 2, Physics question 55

A potential barrier of 0.4 V exists across a p-n junction. An electron enters the junction from the n-side with a speed of 6.0×1056.0\times10^5 ms−1^{-1}. The speed with which electron enters the p side will be x3×105\dfrac x3\times10^5 ms−1^{-1} the value of xx is ______.

(Given mass of electron =9×10−31=9\times10^{-31} kg, charge on electron =1.6×10−19=1.6\times10^{-19} C.)

Answer and worked solution

Official answer: 14

Energy. 12mv2=12×9×10−31×36×1010=1.62×10−19\frac12mv^2=\frac12\times9\times10^{-31}\times36\times10^{10}=1.62\times10^{-19} J; the barrier takes 0.64×10−190.64\times10^{-19} J.

Speed. v2=2×0.98×10−199×10−31≈2.18×1011v^2=\dfrac{2\times0.98\times10^{-19}}{9\times10^{-31}}\approx2.18\times10^{11}, v≈4.67×105=143×105v\approx4.67\times10^5=\frac{14}3\times10^5 m s−1^{-1}.

Answer: 14

Topics:Semiconductors and p-n junction
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