NEET UG 2009 — Physics Modern Physics

De-Broglie wavelength of an electron orbiting in the $n=2$ state of hydrogen atom is close to (Given Bohr radius $=0.052 \mathrm{~nm}$ )

Which of the following options represent the variation of photoelectric current with property of light shown on the x -axis? 

The maximum kinetic energy of photoelectrons from a surface with work function φ = 2 eV when light of λ = 4000 Å falls on it is (hc = 12400 eV·Å):

A full wave rectifier circuit with diodes $\left(D_1\right)$ and $\left(D_2\right)$ is shown in the figure. If input supply voltage $V_{\text {in }}=220 \sin (100 \pi t)$ volt, then at $t=15 \mathrm{msec}$ 

A particle of mass $m$ is moving around the origin with a constant force $F$ pulling it towards the origin. If Bohr model is used to describe its motion, the radius $r$ of the $n^{\text {th }}$ orbit and the particle's speed $v$ in the orbit depend on $n$ as