1
NEET 2022 Phase 2
+4
-1

Let R1 be the radius of the second stationary orbit and R2 be the radius of the fourth stationary orbit of an electron in Bohr's model. The ratio $${{{R_1}} \over {{R_2}}}$$ is :

A
4
B
0.25
C
0.5
D
2
2
NEET 2022 Phase 2
+4
-1

Given below are two statements

Statement I : The law of radioactive decay states that the number of nuclei undergoing the decay per unit time is inversely proportional to the total number of nuclei in the sample.

Statement II : The half of a radionuclide is the sum of the life time of all nuclei, divided by the initial concentration of the nuclei at time t = 0.

In the light of the above statements, choose the most appropriate answer from the options given below :

A
Statement I is incorrect but statement II is correct
B
Both statement I and statement II are correct
C
Both statement I and statement II are incorrect
D
Statement I is correct but statement II is incorrect
3
NEET 2022 Phase 2
+4
-1

At any instant, two elements X1 and X2 have same number of radioactive atoms. If the decay constant of X1 and X2 are 10 $$\lambda$$ and $$\lambda$$ respectively, then the time when the ratio of their atoms becomes $${1 \over e}$$ respectively will be :

A
$${1 \over {5\lambda }}$$
B
$${1 \over {11\lambda }}$$
C
$${1 \over {9\lambda }}$$
D
$${1 \over {6\lambda }}$$
4
NEET 2022 Phase 2
+4
-1

The ratio of Coulomb's electrostatic force to the gravitational force between an electron and a proton separated by some distance is 2.4 $$\times$$ 1039. The ratio of the proportionality constant, $$K = {1 \over {4\pi {\varepsilon _0}}}$$ to the gravitational constant G is nearly (Given that the charge of the proton and electron each = 1.6 $$\times$$ 10$$-$$19 C, the mass of the electron = 9.11 $$\times$$ 10$$-$$31 kg, the mass of the proton = 1.67 $$\times$$ 10$$-$$27 kg) :

A
10
B
1020
C
1030
D
1040
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