1
JEE Main 2022 (Online) 27th June Morning Shift
Numerical
+4
-1
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A beam of monochromatic light is used to excite the electron in Li+ + from the first orbit to the third orbit. The wavelength of monochromatic light is found to be x $$\times$$ 10$$-$$10 m. The value of x is ___________.

[Given hc = 1242 eV nm]

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2
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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3
JEE Main 2021 (Online) 27th August Evening Shift
Numerical
+4
-1
Change Language
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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4
JEE Main 2021 (Online) 27th July Evening Shift
Numerical
+4
-1
Change Language
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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