JEE Mains · Physics · STD 12 - 14. Semicondutor electronics

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 \(6.0 \times 10^{5} \,ms ^{-1}\). The speed with which electron enters the \(p\) side will be \(\frac{x}{3} \times 10^{5} \,ms ^{-1}\) the value of \(x\) is .............. (Given mass of electron \(=9 \times 10^{-31} \,kg\), charge on electron \(=1.6 \times 10^{-19} \,C\).)

A \(11\)
B \(13\)
C \(14\)
D \(20\)

Verified Solution

Answer & Solution

Correct Answer

(C) \(14\)

Step-by-step Solution

Detailed explanation

Work done by Electric field \(=K_{ r }- K _{ I }\) \(\frac{1}{2} mv ^{2}-\frac{1}{2} mu ^{2}=-1.6-10^{-19} \times 0.4\) \(\frac{1}{2} 9 \times 10^{-31}\left( v ^{2}- u ^{2}\right)=-0.64 \times 10^{-19}\) \(u ^{2}- v ^{2}=\frac{2 \times 0.64 \times 10^{12}}{9}\)…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Match List\(-I\) with List\(-II\)

List\(-I\)	List\(-II\)
\((a)\) \(h\) (Planck's constant)	\((i)\) \(\left[ M L T ^{-1}\right]\)
\((b)\) \(E\) (kinetic energy)	\((ii)\) \(\left[ M L ^{2} T ^{-1}\right]\)
\((c)\) \(V\) (electric potential)	\((iii)\) \(\left[ M L ^{2} T ^{-2}\right]\)
\((d)\) \(P\) (linear momentum)	\(( iv )\left[ M L ^{2} I ^{-1} T ^{-3}\right]\)

Choose the correct answer from the options given below

JEE Mains 2021 Medium

Assertion \(A\) : If \(A, B, C, D\) are four points on a semi-circular arc with centre at \('O'\) such that \(|\overrightarrow{{AB}}|=|\overrightarrow{{BC}}|=|\overrightarrow{{CD}}|\), then \(\overrightarrow{{AB}}+\overrightarrow{{AC}}+\overrightarrow{{AD}}=4 \overrightarrow{{AO}}+\overrightarrow{{OB}}+\overrightarrow{{OC}}\) Reason \(R\) : Polygon law of vector addition yields \(\overrightarrow{A B}+\overrightarrow{B C}+\overrightarrow{C D}+\overrightarrow{A D}=2 \overrightarrow{A O}\) In the light of the above statements, choose the most appropriate answer from the options given below

JEE Mains 2021 Hard

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