The Total solution for NCERT class 6-12
Monochromatic radiation of wavelength 640.2nm (1nm = 10−9 m) from a neon lamp irradiates photosensitivematerial made of caesium on tungsten. The stopping voltage is measured to be0.54 V. The source is replaced by an iron source and its 427.2 nm lineirradiates the same photo-cell. Predict the new stopping voltage.
Wavelength of the monochromaticradiation, λ = 640.2 nm
= 640.2 × 10−9 m
Stopping potential of the neon lamp, V0 =0.54 V
Charge on an electron, e =1.6 × 10−19 C
Planck’s constant, h = 6.6× 10−34 Js
We have the photo-energyrelation from the photoelectric effect as:
Wavelength of the radiation emitted from aniron source, λ‘ = 427.2 nm
= 427.2 × 10−9 m
Hence,the new stopping potential is 1.50 eV.