1
JEE Main 2021 (Online) 25th July Morning Shift
+4
-1
Out of Syllabus
Some nuclei of a radioactive material are undergoing radioactive decay. The time gap between the instances when a quarter of the nuclei have decayed and when half of the nuclei have decayed is given as :

(where $$\lambda$$ is the decay constant)
A
$${1 \over 2}{{\ln 2} \over \lambda }$$
B
$${{\ln 2} \over \lambda }$$
C
$${{2\ln 2} \over \lambda }$$
D
$${{\ln {3 \over 2}} \over \lambda }$$
2
JEE Main 2021 (Online) 25th July Morning Shift
+4
-1
Out of Syllabus
The half-life of $${}^{198}Au$$ is 3 days. If atomic weight of $${}^{198}Au$$ is 198 g/mol then the activity of 2 mg of $${}^{198}Au$$ is [in disintegration/second] :
A
2.67 $$\times$$ 1012
B
6.06 $$\times$$ 1018
C
32.36 $$\times$$ 1012
D
16.18 $$\times$$ 1012
3
JEE Main 2021 (Online) 22th July Evening Shift
+4
-1
A nucleus with mass number 184 initially at rest emits an $$\alpha$$-particle. If the Q value of the reaction is 5.5 MeV, calculate the kinetic energy of the $$\alpha$$-particle.
A
5.5 MeV
B
5.0 MeV
C
5.38 MeV
D
0.12 MeV
4
JEE Main 2021 (Online) 20th July Evening Shift
+4
-1
Out of Syllabus
For a certain radioactive process the graph between In R and t(sec) is obtained as shown in the figure. Then the value of half life for the unknown radioactive material is approximately :
A
9.15 sec
B
6.93 sec
C
2.62 sec
D
4.62 sec
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Modern Physics
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