In a photoelectric experiment, the wavelength of the light incident on the metal is changed from 200 nm to 400 nm . The decrease in the stopping potential is close to

[use $h c=1240 \mathrm{eV}$-nm, where $h=$ Planck's constant and $c$ is velocity of light]

The de-Broglie wavelength of an electron with kinetic energy of 320 eV is (take, $h=6.0 \times 10^{-34}$ SI unit, mass of electron $=m_c=9.0 \times 10^{-31} \mathrm{~kg}$, charge of an electron $=1.6 \times 10^{-19} \mathrm{C}$ )

Light strikes a metal surface causing photoelectric emission. The wavelength of incident light is 248 nm . If the stopping potential for the ejected electrons is 2.8 eV , then the work function of the metal is (take, $h c=1240 \mathrm{eV}-\mathrm{nm}$ )

The de-Broglie wavelength associated with an electron, accelerated through a potential difference of 121 V is about

(take, Plank's constant $=h=6.6 \times 10^{-34} \mathrm{Js}$, mass of electron $=9 \times 10^{-31} \mathrm{~kg}$ )