1
JEE Main 2019 (Online) 8th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Radiation coming from transitions n = 2 to n = 1 of hydrogen atoms fall on He+ ions in n = 1 and n = 2 states. The possible transition of helium ions as they absorb energy from the radiation is :
A
n = 1 $$ \to $$ n = 4
B
n = 2 $$ \to $$ n = 5
C
n = 2 $$ \to $$ n = 4
D
n = 2 $$ \to $$ n = 3
2
JEE Main 2019 (Online) 12th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
In a radioactive decay chain, the initial nucleus is $${}_{90}^{232}$$Th. At the end there are 6 $$\alpha $$-particles and 4 $$\beta $$-particles which are emitted. If the end nucleus is $${}_Z^A$$X, A and Z are given by :
A
A = 208; Z = 80
B
A = 208; Z = 82
C
A = 200; Z = 81
D
A = 202; Z = 80
3
JEE Main 2019 (Online) 12th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
A particle of mass m moves in a circular orbit in a central potential field U(r) = $${1 \over 2}$$ kr2. If Bohr 's quantization conditions are applied, radii of possible orbitls and energy levels vary with quantum number n as :
A
rn $$ \propto $$ $$\sqrt n $$, En $$ \propto $$ n
B
rn $$ \propto $$ $$\sqrt n $$, En $$ \propto $$ $${1 \over n}$$
C
rn $$ \propto $$ n, En $$ \propto $$ n
D
rn $$ \propto $$ n2, En $$ \propto $$ $${1 \over {{n^2}}}$$
4
JEE Main 2019 (Online) 11th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
In a hydrogen like atom, when an electron jumps from the M-shell to the L-shell, the wavelength of emitted radiation is $$\lambda $$. If an electron jumps from N-shell to the L-shell, the wavelength of emitted radiation will be:
A
$${{25} \over {16}}$$ $$\lambda $$
B
$${{27} \over {20}}$$ $$\lambda $$
C
$${{16} \over {25}}$$ $$\lambda $$
D
$${{20} \over {27}}$$ $$\lambda $$
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