1
JEE Main 2022 (Online) 24th June Evening Shift
Numerical
+4
-1
Out of Syllabus
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A sample contains 10$$-$$2 kg each of two substances A and B with half lives 4 s and 8 s respectively. The ratio of their atomic weights is 1 : 2. The ratio of the amounts of A and B after 16 s is $${x \over {100}}$$. The value of x is ___________.

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2
JEE Main 2021 (Online) 27th August Evening Shift
Numerical
+4
-1
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X different wavelengths may be observed in the spectrum from a hydrogen sample if the atoms are exited to states with principal quantum number n = 6 ? The value of X is ______________.
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3
JEE Main 2021 (Online) 27th July Evening Shift
Numerical
+4
-1
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The K$$\alpha$$ X-ray of molybdenum has wavelength 0.071 nm. If the energy of a molybdenum atoms with a K electron knocked out is 27.5 keV, the energy of this atom when an L electron is knocked out will be __________ keV. (Round off to the nearest integer)

[h = 4.14 $$\times$$ 10$$-$$15 eVs, c = 3 $$\times$$ 108 ms$$-$$1]
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4
JEE Main 2021 (Online) 27th July Morning Shift
Numerical
+4
-1
Change Language
In Bohr's atomic model, the electron is assumed to revolve in a circular orbit of radius 0.5 $$\mathop A\limits^o $$. If the speed of electron is 2.2 $$\times$$ 166 m/s, then the current associated with the electron will be _____________ $$\times$$ 10$$-$$2 mA. [Take $$\pi$$ as $${{22} \over 7}$$]
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