When radiation of wavelength $\mathrm{\lambda }$ is incident on a metallic surface, the stopping potential is 4.8 volts. If the same surface is illuminated with radiation of double the wavelength, then the stopping potential becomes 1.6 volts. Then the threshold wavelength for the surface is

(a) $2\mathrm{\lambda }$                 (b) $4\mathrm{\lambda }$
(c) $6\mathrm{\lambda }$                 (d) $8\mathrm{\lambda }$

If the energy of the photon is increased by a factor of 4, then its momentum 

(1) Does not change

(2) Decreases by a factor of 4

(3) Increases by a factor of 4

(4) Decreases by a factor of 2

In a photoemissive cell with executing wavelength $\mathrm{\lambda }$, the fastest electron has speed v. If the exciting wavelength is changed to 3$\mathrm{\lambda }$/4, the speed of the fastest emitted electron will be 
(a) $\mathrm{v}{\left(3/4\right)}^{1/2}$                              (b) $\mathrm{v}{\left(4/3\right)}^{1/2}$
(c) Less than $\mathrm{v}{\left(4/3\right)}^{1/2}$               (d) Greater than $\mathrm{v}{\left(4/3\right)}^{1/2}$

The figure shows the variation of photocurrent with anode potential for a photo-sensitive surface for three different radiations. Let ${\mathrm{I}}_{\mathrm{a}},{\mathrm{I}}_{\mathrm{b}}$ and ${\mathrm{I}}_{\mathrm{c}}$ be the intensities and ${\mathrm{f}}_{\mathrm{a}},{\mathrm{f}}_{\mathrm{b}}$ and ${\mathrm{f}}_{\mathrm{c}}$ be the frequencies for the curves a, b and c respectively. Then-

1. ${\mathrm{f}}_{\mathrm{a}}={\mathrm{f}}_{\mathrm{b}} \mathrm{and} {\mathrm{I}}_{\mathrm{a}}\ne {\mathrm{I}}_{\mathrm{b}}$ 
2. ${\mathrm{f}}_{\mathrm{a}}={\mathrm{f}}_{\mathrm{c}} \mathrm{and} {\mathrm{I}}_{\mathrm{a}}={\mathrm{I}}_{\mathrm{c}}$
3. ${\mathrm{f}}_{\mathrm{a}}={\mathrm{f}}_{\mathrm{b}} \mathrm{and} {\mathrm{I}}_{\mathrm{a}}={\mathrm{I}}_{\mathrm{c}}$
4. ${\mathrm{f}}_{\mathrm{a}}={\mathrm{f}}_{\mathrm{b}} \mathrm{and} {\mathrm{I}}_{\mathrm{a}}={\mathrm{I}}_{\mathrm{b}}$

The stopping potential as a function of the frequency of the incident radiation is plotted for two different photoelectric surfaces \(A\) and \(B\). The graphs demonstrate that \(A\)'s work function is:

The value of stopping potential in the following diagram is given by:
    

Figure represents a graph of kinetic energy (K) of photoelectrons (in eV) and frequency (v) for a metal used as cathode in photoelectric experiment. The work function of metal is

1. 1 eV

2. 1.5 eV

3. 2 eV

4. 3 eV

The dependence of the short wavelength limit ${\mathrm{\lambda }}_{\min }$ on the accelerating potential V is represented by the curve of figure:

1. A
2. B
3. C
4. None of these

The energy that should be added to an electron, to reduce its de-Broglie wavelengths from ${10}^{-10}$ m to 0.5 x ${10}^{-10}$ m, will be

(1) four times the initial energy

(2) thrice the initial energy

(3) equal to the initial energy

(4) twice the initial energy