1
JEE Main 2021 (Online) 20th July Evening Shift
Numerical
+4
-1
Out of Syllabus
A radioactive substance decays to $${\left( {{1 \over {16}}} \right)^{th}}$$ of its initial activity in 80 days. The half life of the radioactive substance expressed in days is ____________.
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2
JEE Main 2021 (Online) 17th March Evening Shift
Numerical
+4
-1
A particle of mass m moves in a circular orbit in a
central potential field U(r) = U0r4. If Bohr's quantization conditions
are applied, radii of possible
orbitals rn vary with $${n^{{1 \over \alpha }}}$$, where $$\alpha$$ is ____________.
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3
JEE Main 2021 (Online) 16th March Morning Shift
Numerical
+4
-1
The first three spectral lines of H-atom in the Balmer series are
given $$\lambda$$1, $$\lambda$$2, $$\lambda$$3 considering the Bohr atomic model, the wave lengths of first and third spectral lines $$\left( \frac{\lambda_{1} }{\lambda_{3} } \right) $$ are related by a factor of approximately 'x' $$\times$$ 10$$-$$1.

The value of x, to the nearest integer, is _________.
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4
JEE Main 2020 (Online) 5th September Morning Slot
Numerical
+4
-0
A particle of mass 200 MeV/c2 collides with a hydrogen atom at rest. Soon after the collision the particle comes to rest, and the atom recoils and goes to its first excited state. The initial kinetic energy of the particle (in eV) is
$${N \over 4}$$. The value of N is :
(Given the mass of the hydrogen atom to be 1 GeV/c2) ______ .
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