Photoelectric effect experiments are performed using three different metal plates p,q and r having work functions ϕp=2.0 eV,ϕq=2.5 eV and ϕr=3.0 eV, respectively. A light beam containing wavelengths of 550 nm, 450 nm and 350 nm with equal intensties illuminates each of the plates. The correct I-V graph for the experiment is (IIT-JEE-2009)
Photoelectric effect experiments are performed using three different metal plates p,q and r having work functions ϕp=2.0 eV,ϕq=2.5 eV and ϕr=3.0 eV, respectively. A light beam containing wavelengths of 550 nm, 450 nm and 350 nm with equal intensties illuminates each of the plates. The correct I-V graph for the experiment is (IIT-JEE-2009)
The correct option is A
Given ϕp=2.0 eV,ϕq=2.5 eV and ϕr=3.0 eV
From the above we can find the cutoff wavelength for each plate λp = 621 nm, λq = 496 nm and λr = 414 nm
It's mentioned that each plate is illuminated by a light that consists of 3 different wavelengths i.e. 550nm, 450nm, 350nm of equal intensities.
Now since the cut off wavelength of plate p is higher than all 3 incident wavelengths so all 3 types of photons will contribute to photoelectrons. Whereas in the case of plate q incident photons of wavelength 450 nm won't be able to contribute in photocurrent as it is higher than it's cut off wavelength of 496 nm. So naturally its photo current will be lesser than the plate p since its being excited by only 2 wavelegths. In case of plate r, 2 incident wavelengths i.e. 550 nm and 450 nm won't be able to excite the photo electrons. Hnece its photocurrent will be only due to photon of wavelength 350 nm and hence will be least.
Ip <Iq < Ir
Given ϕp=2.0 eV,ϕq=2.5 eV and ϕr=3.0 eV
From the above we can find the cutoff wavelength for each plate λp = 621 nm, λq = 496 nm and λr = 414 nm
It's mentioned that each plate is illuminated by a light that consists of 3 different wavelengths i.e. 550nm, 450nm, 350nm of equal intensities.
Now since the cut off wavelength of plate p is higher than all 3 incident wavelengths so all 3 types of photons will contribute to photoelectrons. Whereas in the case of plate q incident photons of wavelength 450 nm won't be able to contribute in photocurrent as it is higher than it's cut off wavelength of 496 nm. So naturally its photo current will be lesser than the plate p since its being excited by only 2 wavelegths. In case of plate r, 2 incident wavelengths i.e. 550 nm and 450 nm won't be able to excite the photo electrons. Hnece its photocurrent will be only due to photon of wavelength 350 nm and hence will be least.
Ip <Iq < Ir
