The number of photo-electrons emitted per second from a metal surface increases when:

1.	The energy of incident photons increases.	2.	The frequency of incident light increases.
3.	The wavelength of the incident light increases.	4.	The intensity of the incident light increases.

The work function of metal is 1 eV. Light of wavelength 3000 Å is incident on this metal surface. The velocity of emitted photo-electrons will be
(a) 10 m/sec                           (b) $1\times {10}^3$ m/sec
(c) $1\times {10}^4$ m/sec                     (d) $1\times {10}^6$ m/sec

The work function of a metal is $1.6\times {10}^{-19}$ J. When the metal surface is illuminated by the light of wavelength 6400 Å, then the maximum kinetic energy of emitted photo-electrons will be
(Planck's constant = $6.4\times {10}^{-34 }\mathrm{Js}$) 
(a) $14\times {10}^{-19} \mathrm{J}$                 (b) $2.8\times {10}^{-19} \mathrm{J}$ 
(c) $1.4\times {10}^{-19} \mathrm{J}$                (d) $1.4\times {10}^{-19} \mathrm{eV}$

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