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?

When light falls on a metal surface,the maximum kinetic energy of the emitted photo-electrons depends upon

In a photoelectric experiment for $4000 \, \mathring{A}$ incident radiation,the potential difference to stop the ejection is $2 \, V$. If the incident light is changed to $3000 \, \mathring{A}$,then the potential required to stop the ejection of electrons will be

In a photoelectric experiment,electrons are ejected from metals $X$ and $Y$ by light of intensity $I$ and frequency $f$. The potential difference $V$ required to stop the electrons is measured for various frequencies. If $Y$ has a greater work function than $X$,which one of the following graphs best illustrates the expected results?

Light of wavelength $\lambda$ strikes a photoelectric surface and electrons are ejected with kinetic energy $K$. If $K$ is to be increased to twice its original value,the wavelength must be changed to $\lambda'$ such that :-

$A$ certain metallic surface is illuminated with monochromatic light of wavelength $\lambda$. The stopping potential for the photoelectric current for this light is $3V_0$. If the same surface is illuminated with light of wavelength $2\lambda$,the stopping potential is $V_0$. The threshold wavelength for this surface for the photoelectric effect is: