Question 138: Dual Nature of Matter and Radiation

Question

A metal exposed to light of wavelength $$800 \mathrm{~nm}$$ and and emits photoelectrons with a certain kinetic energy. The maximum kinetic energy of photo-electron doubles when light of wavelength $$500 \mathrm{~nm}$$ is used. The workfunction of the metal is : (Take hc $$=1230 \,\mathrm{eV}-\mathrm{nm}$$ ).

Accepted Answer

$$\because$$ $${K_m} = {{hc} \over \lambda } - \phi $$
$$ \Rightarrow K = {{1230} \over {800}} - \phi $$
and, $$2K = {{1230} \over {500}} - \phi $$
$$ \Rightarrow 2 	imes {{1230} \over {800}} - 2\phi  = {{1230} \over {500}} - \phi $$
$$ \Rightarrow \phi  = 0.615\,eV$$

Answer

1.537 eV

Answer

2.46 eV

Answer

0.615 eV

Answer

1.23 eV

Dual Nature of Matter and Radiation

A metal exposed to light of wavelength $800 \mathrm{~nm} and and emits photoelectrons with a certain kinetic energy. The maximum kinetic energy of photo-electron doubles when light of wavelength 500 \mathrm{~nm} is used. The workfunction of the metal is : (Take hc =1230 \,\mathrm{eV}-\mathrm{nm}$ ).

Choose the correct answer: