1
JEE Main 2021 (Online) 20th July Evening Shift
Numerical
+4
-1
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 ____________.
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
orbitals rn vary with $${n^{{1 \over \alpha }}}$$, where $$\alpha$$ is ____________.
3
JEE Main 2021 (Online) 16th March Morning Shift
Numerical
+4
-1
The first 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 _________.
4
JEE Main 2021 (Online) 25th February Evening Shift
Numerical
+4
-1
The wavelength of an X-ray beam is 10$$\mathop A\limits^o$$. The mass of a fictitious particle having the same energy as that of the X-ray photons is $${x \over 3}h$$ kg. The value of x is __________. (h = Planck's constant)
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