$A$ point source of light is used in a photoelectric effect experiment. If the source is moved farther from the emitting metal, then the stopping potential will

The following graph shows the variation of stopping potential with the frequency of incident radiation $(v)$ for a given metal. The correct variation is shown in graph [$v_0 =$ threshold frequency].

At an incident radiation frequency of $v_1$,which is greater than the threshold frequency,the stopping potential for a certain metal is $V_1$. At frequency $2 v_1$,the stopping potential is $3 V_1$. If the stopping potential at frequency $4 v_1$ is $n V_1$,then $n$ is

When a metallic surface is illuminated with radiation of wavelength $\lambda$,the stopping potential is $V$. If the same surface is illuminated with radiation of wavelength $2\lambda$,the stopping potential is $\frac{V}{4}$. The threshold wavelength for the metallic surface is:

In a photocell circuit,the stopping potential $V_0$ is a measure of the maximum kinetic energy of the photoelectrons. The following graph shows experimentally measured values of stopping potential versus frequency $\nu$ of incident light. The values of Planck's constant and the work function as determined from the graph are (taking the magnitude of electronic charge to be $e = 1.6 \times 10^{-19} \, C$):

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