When light of frequency twice the threshold frequency is incident on a metal plate,the maximum velocity of the emitted electron is $v_{1}$. When the frequency of incident radiation is increased to five times the threshold value,the maximum velocity of the emitted electron becomes $v_{2}$. If $v_{2} = x v_{1}$,the value of $x$ will be...........

In a photoelectric experiment,a monochromatic light is incident on the emitter plate $E$,as shown in the figure. When switch $S_1$ is closed and switch $S_2$ is open,the photoelectrons strike the collector plate $C$ with a maximum kinetic energy of $1 eV$. If switch $S_1$ is open and switch $S_2$ is closed and the frequency of the incident light is doubled,the photoelectrons strike the collector plate with a maximum kinetic energy of $20 eV$. The threshold wavelength of the emitter plate is (in $Å$)

The threshold wavelength for photoelectric emission from a metal surface is $5200 \ \mathring A$. Which of the following sources will cause photoelectric emission from this surface?

The photoelectric threshold wavelength for potassium (work function being $2 \ eV$) is ........... $nm$.

$A$ Hydrogen-like atom has atomic number $Z$. Photons emitted in the electronic transitions from level $n=4$ to level $n=3$ in these atoms are used to perform a photoelectric effect experiment on a target metal. The maximum kinetic energy of the photoelectrons generated is $1.95 \ eV$. If the photoelectric threshold wavelength for the target metal is $310 \ nm$,the value of $Z$ is:

The figure shows the variation of photocurrent with anode potential for four different radiations. Let $f_a$,$f_b$,$f_c$ and $f_d$ be the frequencies for the curves $a$,$b$,$c$ and $d$ respectively.