SATHEE: General Physics Question 3

General Physics Question 3

Question 3

In an experiment, the initial number of radioactive nuclei is 3000. It is found that $1000 \pm 40$ nuclei decayed in the first 1.0s. For $| x | ≪ 1, \ln (1 + x) = x$ up to first power in $x$ . The error $Δ λ$ , in the determination of the decay constant $λ$ in $s^{- 1}$ , is (a) 0.04 (b) 0.03 (c) 0.02 (d) 0.01

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A dense collection of equal number of electrons and positive ions is called neutral plasma. Certain solids containing fixed positive ions surrounded by free electrons can be treated as neutral plasma. Let $N$ be the number density of free electrons, each of mass $m$ . When the electrons are subjected to an electric field, they are displaced relatively away from the heavy positive ions. If the electric field becomes zero, the electrons begin to oscillate about the positive ions with a natural angular frequency $ω_{p}$ , which is called the plasma frequency.

To sustain the oscillations, a time varying electric field needs to be applied that has an angular frequency $ω$ , where a part of the energy is absorbed and a part of it is reflected. As $ω$ approaches $ω_{p}$ , all the free electrons are set to resonance together and all the energy is reflected. This is the explanation of high reflectivity of metals.

(2011)

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Answer:

Correct Answer: 4. (c)

Solution:

$N = N_{0} e^{- λ t}$

$In N = In N_{0} - λ t$

Differentiating w.r.t $λ$ , we get

$\begin{array}{cc} \frac{1}{N} \cdot \frac{d N}{d λ} = 0 - t \Rightarrow & | d λ | = \frac{d N}{N t} = \frac{40}{2000 \times 1} = 0.02 \end{array}$

General Physics Question 3

Question 3

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General Physics Question 3

Question 3

Passage

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

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