JEE MAIN - Physics (2025 - 22nd January Morning Shift - No. 8)
The work functions of cesium (Cs) and lithium (Li) metals are 1.9 eV and 2.5 eV , respectively. If we incident a light of wavelength 550 nm on these two metal surfaces, then photo-electric effect is possible for the case of
Both Cs and Li
Neither Cs nor Li
Li only
Cs only
คำอธิบาย
For photo-electric effect, energy of the photon must be greater than the work function of the metal.
We know, $$E = {{1240} \over \lambda } = {{1240} \over {550}}$$ (as $\lambda=550$ nm given)
$\Rightarrow E=2.25$ eV
here, $$E > {\phi _{cs}}$$
So, $C_S$ only.