1
JEE Main 2021 (Online) 16th March Morning Shift
Numerical
+4
-1
When light of wavelength 248 nm falls on a metal of threshold energy 3.0 eV, the de-Broglie wavelength of emitted electrons is _______$$\mathop A\limits^o $$. (Round off to the Nearest Integer).

[ Use : $$\sqrt 3 $$ = 1.73, h = 6.63 $$\times$$ 10$$-$$34 Js

me = 9.1 $$\times$$ 10$$-$$31 kg; c = 3.0 $$\times$$ 108 ms$$-$$1; 1eV = 1.6 $$\times$$ 10$$-$$19 J]
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2
JEE Main 2021 (Online) 26th February Evening Shift
Numerical
+4
-1
A ball weighing 10 g is moving with a velocity of 90 ms$$-$$1. If the uncertainty in its velocity is 5%, then the uncertainty in its position is ___________ $$\times$$ 10$$-$$33 m. (Rounded off to the nearest integer)

[Given : h = 6.63 $$\times$$ 10$$-$$34 Js]
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3
JEE Main 2021 (Online) 24th February Morning Shift
Numerical
+4
-1
Change Language
A proton and a Li3+ nucleus are accelerated by the same potential. If $$\lambda _{Li}$$ and $$\lambda _p$$ denote the de Broglie wavelengths of Li3+ and proton respectively, then the value of $${{{\lambda _{Li}}} \over {{\lambda _p}}}$$ is x $$ \times $$ 10-1.
The value of x is ______. (Rounded off to the nearest integer)
[Mass of Li3+ = 8.3 mass of proton]
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4
JEE Main 2020 (Online) 2nd September Evening Slot
Numerical
+4
-0
The work function of sodium metal is 4.41 $$ \times $$ 10–19 J. If photons of wavelength 300 nm are incident on the metal, the kinetic energy of the ejected electrons will be (h = 6.63 $$ \times $$ 10–34 J s; c = 3 $$ \times $$ 108 m/s) ________ × 10–21 J.
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