11.6 In an experiment on photoelectric effect, the slope of the cut-off voltage versus frequency of incident light is found to be 4.12 $*\mathit{}{10}^{-15}$ Vs. Calculate the value of Planck's constant.

Given below are two statements:

Statement I : Davission-Germer experiment establishes, the wave nature of electrons.

Statement II : If electrons have wave nature, they can interfere and show diffraction.

In the light of the above statements choose the correct answer from the option given below:

Radiation from hydrogen gas excited to first excited state is used for illuminating certain metallic plate. When the same plate is exposed to the radiation from some unknown hydrogen like gas excited to the same level it is found that de-Broglie wavelength of fastest photoelectron has decreased by 2.3 times. It is given that energy corresponding to longest wavelength of Lyman series of the unknown gas is 3 times the ionization energy of hydrogen gas (13.6eV). The work function (in eV) of the metallic plate is ______. [Take (2.3)² = 5.25]

A metal exposed to light of wavelength 800nm and emits photoelectrons with a certain kinetic energy. The maximum kinetic energy of photo-electron doubles when light of wavelength 500nm is used. The work function of the metal is: (Take hc = 1230 eV –nm).

When light of frequency twice the threshold frequency is incident on the metal plate, the maximum velocity of emitted electron is ${\upsilon }_1.$ <!-- [if gte mso 9]><xml> </xml><![endif]-->When the frequency of incident radiation is increased to five times the threshold value, the maximum velocity of emitted electron becomes ${\upsilon }_2.$ If ${\upsilon }_2=x{\upsilon }_1,$ <!-- [if gte mso 9]><xml> </xml><![endif]-->the value of x will be __________.             

Kindly consider the following

$f\left(x\right)=\{\begin{array}{cc}\hfill \frac{2x^2-3x+2}{x-2},\hfill & \hfill x\ne 2\hfill \\ \hfill 5,\hfill & \hfill x=2\hfill \end{array}$