For a metal of work function 6.6 eV , which of the following wavelengths of incident radiation does not give rise to the photoelectric effect?

(Take Planck's constant as $6.6 \times 10^{-34} \mathrm{~J} \mathrm{~s}$ )

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?

A photon and an electron (mass $m$ ) have the same energy $E$. The ratio ( $\lambda_{\text {photon }} / \lambda_{\text {electron }}$ ) of their de Broglie wavelengths is: ( $c$ is the speed of light)