Question 283: Dual Nature of Matter and Radiation

Question

On a photosensitive material, when frequency of incident radiation is increased by $20 \%$, maximum kinetic energy of emitted photoelectrons increases from 0.4 eV to 0.7 eV . The work function of the material is

Accepted Answer

We use Einstein's Photoelectric Equation:
$$ 	ext{K.E.} = h f - \phi $$
Let the original frequency of light be $f$. After a $20\%$ increase, the new frequency becomes $1.2f$.
For the first case (original frequency):
$$ \mathrm{K}_1 = h f - \phi = 0.4\ 	ext{eV} $$
For the second case (increased frequency):
$$ \mathrm{K}_2 = h 	imes 1.2f - \phi = 0.7\ 	ext{eV} $$
Subtract the first equation from the second to find $hf$:
$$ [h 	imes 1.2f - \phi] - [hf - \phi] = 0.7 - 0.4 $$
This simplifies to:
$$ 0.2hf = 0.3 $$
So,
$$ hf = \frac{0.3}{0.2} = 1.5\ 	ext{eV} $$
Now, use $hf$ to find the work function $\phi$:
$$ \phi = hf - 0.4 = 1.5 - 0.4 = 1.1\ 	ext{eV} $$

Answer

3.5 eV

Answer

1.1 eV

Answer

0.48 eV

Answer

0.22 eV

Dual Nature of Matter and Radiation

On a photosensitive material, when frequency of incident radiation is increased by 20 \%, maximum kinetic energy of emitted photoelectrons increases from 0.4 eV to 0.7 eV . The work function of the material is

Choose the correct answer: