1
JEE Main 2020 (Online) 3rd September Evening Slot
+4
-1
The radius R of a nucleus of mass number A can be estimated by the formula
R = (1.3 $$\times$$ 10–15)A1/3 m.
It follows that the mass density of a nucleus is of the order of :

(Mprot. $$\cong$$ Mneut $$\simeq$$ 1.67 $$\times$$ 10–27 kg)
A
1024 kg m–3
B
1010 kg m–3
C
1017 kg m–3
D
103 kg m–3
2
JEE Main 2020 (Online) 3rd September Evening Slot
+4
-1
Hydrogen ion and singly ionized helium atom are accelerated, from rest, through the same potential difference. The ratio of final speeds of hydrogen and helium ions is close to :
A
2 : 1
B
1 : 2
C
5 : 7
D
10 : 7
3
JEE Main 2020 (Online) 3rd September Morning Slot
+4
-1
In a radioactive material, fraction of active material remaining after time t is 9/16. The fraction that was remaining after t/2 is
A
$${3 \over 4}$$
B
$${4 \over 5}$$
C
$${3 \over 5}$$
D
$${7 \over 8}$$
4
JEE Main 2020 (Online) 2nd September Evening Slot
+4
-1
In a hydrogen atom the electron makes a transition from (n + 1)th level to the nth level. If n >> 1, the frequency of radiation emitted is proportional to :
A
$${1 \over n}$$
B
$${1 \over {{n^2}}}$$
C
$${1 \over {{n^3}}}$$
D
$${1 \over {{n^4}}}$$
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