If an electron approaches the p-n junction from the n-side with a speed of 5 × 105 m s-1, with what speed will it enter the p-side?

Question

If an electron approaches the p-n junction from the n-side with a speed of 5 × 105 m s-1, with what speed will it enter the p-side? (A) 5× 105 m/s (B) 2.5× 106 m/s (C) 2.7× 105 m/s (D) 1× 105 m/s

Tardigrade Admin · Accepted Answer

Suppose an electron enters the depletion layer with speed

v_{1}

and

p

-region with speed

v_{2}

, as shown in figure.

potential energy increased by

e V

joule.
By energy conservation;

\frac{1}{2} m v_{2}^{2} + e V = \frac{1}{2} m v_{1}^{2}

or

\frac{1}{2} m v_{2}^{2} = \frac{1}{2} m v_{1}^{2} - e V

= \frac{1}{2} \times 9.1 \times 1 0^{- 31} (5.0 \times 1 0^{5})^{2} - 1.6 \times 1 0^{- 19} \times 0.50

= (1.13 - 0.8) \times 1 0^{- 19}

= 0.33 \times 1 0^{- 19} J

= V_{2}^{2} = \frac{2 \times 0.33 \times 1 0 ^{- 19}}{m}

= \frac{0.66 \times 1 0 ^{- 19}}{9.1 \times 1 0 ^{- 31}}

= 7.25 \times 1 0^{10}

or

v_{2} = 2.7 \times 1 0^{5} m s^{- 1}

Q. If an electron approaches the $p - n$ junction from the $n$ -side with a speed of $5 \times 1 0^{5} m s^{- 1}$ , with what speed will it enter the $p$ -side?

$5 \times 1 0^{5} m / s$

$2.5 \times 1 0^{6} m / s$

$2.7 \times 1 0^{5} m / s$

$1 \times 1 0^{5} m / s$

Q. If an electron approaches the p−n junction from the n-side with a speed of 5×105ms−1, with what speed will it enter the p-side?

5×105m/s

2.5×106m/s

2.7×105m/s

1×105m/s

Q. If an electron approaches the $p - n$ junction from the $n$ -side with a speed of $5 \times 1 0^{5} m s^{- 1}$ , with what speed will it enter the $p$ -side?

$5 \times 1 0^{5} m / s$

$2.5 \times 1 0^{6} m / s$

$2.7 \times 1 0^{5} m / s$

$1 \times 1 0^{5} m / s$