$\mathrm{U}.\mathrm{V}.$ light of wavelength $800 \mathrm{A}° \& 700 \mathrm{A}°$ falls on two hydrogen atoms in their ground state  $\&$ liberates electrons with kinetic energy $1.8 \mathrm{eV}$ and $4 \mathrm{eV}$ respectively. If Planck's constant is $\mathrm{y}\times {10}^{-34} \mathrm{Js}.$ Then find value of $\mathrm{y}.$ Round off your answer to the nearest integer.

A potential difference of $20 \mathrm{kV}$ is applied across an $\mathrm{X}$-ray tube. The minimum wavelength (in $\stackrel{\circ }{\mathrm{A}}$) of $\mathrm{X}$-ray generated is $\frac{\mathrm{a}}{100}$. The value of $\mathrm{a}$ is

Given: Planck's constant: $6.626\times {10}^{-34}\mathrm{Js}$

Round of the answer to the nearest integer.

Iodine molecule dissociates into atoms after absorbing light of $4500{ \mathrm{A}}^0$. If one quantum of radiation is absorbed by each molecule, if $\mathrm{K}.\mathrm{E}.$ of iodine atoms is $\mathrm{y}\times {10}^{-20} \mathrm{J}.$ Then find value of $\mathrm{y}.$

(Bond energy of ${\mathrm{I}}_2=240 \mathrm{kJ}/\mathrm{mol}$ )

Suppose ${10}^{-17} \mathrm{J}$ of light energy is needed by the interior of the human eye to see an object. How many photons of green light $\left(\mathrm{\lambda }=550 \mathrm{nm}\right)$ are needed to generate this minimum amount of energy?

Given :$\frac{\mathrm{hc}}{\mathrm{\lambda }}=\frac{{\displaystyle 1240}}{{\displaystyle \mathrm{\lambda } \mathrm{in} \mathrm{nm}}}$

${10}^{\mathrm{x}}$ number of photons of radiation of frequency $5\times {10}^{13}{ \mathrm{s}}^{-1}$ that must be absorbed in order to melt one $\mathrm{g}$ ice when the latent heat of fusion of ice is $330 \mathrm{J}/\mathrm{g}.$ Find value of $\mathrm{x}.$

Use: Planck's constant $=6.626\times {10}^{-34}\mathrm{Js}$

If threshold frequency of metal is $4.5\times {10}^{\mathrm{x}}{\sec }^{-1}$ and binding energy is $180.69 \mathrm{kJ}{ \mathrm{mol}}^{-1}$ of electron. Then find value of $\mathrm{x}$.

Use: Planck's constant $=6.626\times {10}^{-34}\mathrm{Js}$