Dual Nature of Radiation and Matter - Result Question 20

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21. An ionization chamber with parallel conducting plates as anode and cathode has $5 \times 10^{7}$ electrons and the same number of singly charged positive ions per $cm^{3}$. The electrons are moving towards the anode with velocity $0.4 m / s$. The current density from anode to cathode is $4 \mu A$ / $m^{2}$. The velocity of positive ions moving towards cathode is

======= ####21. An ionization chamber with parallel conducting plates as anode and cathode has $5 \times 10^{7}$ electrons and the same number of singly charged positive ions per $cm^{3}$. The electrons are moving towards the anode with velocity $0.4 m / s$. The current density from anode to cathode is $4 \mu A$ / $m^{2}$. The velocity of positive ions moving towards cathode is

3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed:content/english/neet-pyq-chapterwise/physics/dual-nature-of-radiation-and-matter/dual-nature-of-radiation-and-matter—result-question-20.md (a) $0.4 m / s$

(b) $1.6 m / s$

(c) zero

(d) $0.1 m / s$

[1992]

Topic 2: Electron Emission, Photon

Photoelectric Effect & X-ray22. Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and intensity is doubled?

(a) four times

(b) one-fourth

(c) zero

(d) doubled

[2020]

Show Answer

Answer:

Correct Answer: 21. (d)

Solution:

  1. (d) Current $=I_e+I_p$

$I_e$ and $I_p$ are current due to electrons and positively charged ions.

$I=n e A V_d$

where,

$ \begin{aligned} n=5 \times 10^{7} / cm^{3}= & 5 \times 10^{7} \times 10^{6} / m^{3} \\ & =5 \times 10^{13} / m^{3} \end{aligned} $

$I_e=5 \times 10^{13} \times 1.6 \times 10^{-19} \times A \times 0.4$

$I_p=5 \times 10^{13} \times 1.6 \times 10^{-19} \times A \times v$

$I=I_e+I_p$ (from equation (i))

$=5 \times 10^{13} \times 1.6 \times 10^{-19} \times A(v+0.4)$

Given, $I / A=4 \times 10^{-6} A / m^{2}$

$4 \times 10^{-6} \times A=5 \times 10^{-6} \times 1.6 \times A(v+0.4)$

$\frac{4}{8}=v+0.4 \Rightarrow 0.5=v+0.4 \Rightarrow v=0.1 m / s$