Light consisting of wavelengths 4000 A° & 6000 A° is incident on a double slit of separation 0.1mm kept at a distance of Im from a screen.
A small rectangular photodetector, 2mm x 10 mm in size, of efficiency 20% and work function 2.2 eV is placed lengthwise. parallel to the fringes. The photoelectrons constituting the current are swept off and the photo current (ip) is allowed to pass through the circuit shown in the diagram.
The photocurrent i$_p$,given that intensity of light at the maximum of the central fringe is 155W/m$^2$ due to each wavelength and the photodetector is placed at a position where the current i$_p$ is maximum. Assume that all photoelectrons have the same energy and that the extemal voltage is sufficient to sweep all the photoelectrons to form the current.
We have to find the charge deposited on the capacitor C ( =120 u F) in 2 secs after the source of light (of both wavelengths) is switched on.
I tried as
Now how can I proceed.