Ultraviolet radiations of 6.2 eV falls on an aluminium surface (work function 4.2 eV ). The kinetic energy in joules of the fastest electron emitted is approximately
1. $3.2\times {10}^{-21}$             

2. $3.2\times {10}^{-19}$

3. $3.2\times {10}^{-17}$             

4. $3.2\times {10}^{-15}$

The work function for tungsten and sodium are 4.5 eV and 2.3 eV respectively. If the threshold wavelength $\mathrm{\lambda }$ for sodium is 5460 Å, the value of $\mathrm{\lambda }$ for tungsten is

(1) 5893 Å                   

(2) 10683 Å

(3) 2791 Å                   

(4) 528 Å

The photoelectric threshold wavelength for a metal surface is 6600 Å. The work function for this is 
(1) 1.87 V                             

(2) 1.87 eV

(3) 18.7 eV                             

(4) 0.18 eV

Photoelectric effect was successfully explained first by
(1) Planck               

(2) Hallwash

(3) Hertz                 

(4) Einstein

Light of wavelength \(4000~\mathrm{\mathring{A}}\) is incident on a sodium surface for which the threshold wavelength of photoelectrons is \(5420~\mathrm{\mathring{A}}\). The work function of sodium is:
1. \(4.58\) eV
2. \(2.29\) eV
3. \(1.14\) eV
4. \(0.57\) eV

Photocell is a device to: 

(1) Store photons

(2) Measure light intensity

(3) Convert photon energy into mechanical energy

(4) Store electrical energy for replacing storage batteries

If the work function for a certain metal is $3.2\times {10}^{-19}$ joule and it is illuminated with light of frequency $8\times {10}^{14}$ Hz. The maximum kinetic energy of the photo-electrons would be $\left(\mathrm{h}=6.63\times {10}^{-34} \mathrm{Js}\right)$

(a) $2.1\times {10}^{-19} \mathrm{J}$              (b) $8.5\times {10}^{-19} \mathrm{J}$ 
(c) $5.3\times {10}^{-19} \mathrm{J}$              (d) $3.2\times {10}^{-19 }\mathrm{J}$