Modern Physics Ques 80
- The work function of a substance is $4.0 $ $eV$. The longest wavelength of light that can cause photoelectron emission from this substance is approximately
$(1998,2 M)$
(a) $540 $ $nm$
(b) $400 $ $nm$
(c) $310 $ $nm$
(d) $220 $ $nm$
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Answer:
Correct Answer: 80.(c)
Solution:
Formula:
- $\lambda($ in $\AA)=\frac{12375}{W(eV)}=\frac{12375}{4.0} \AA \approx 3093 $ $\AA$
or $\lambda \approx 309.3 $ $nm \approx 310 $ $nm$
NOTE: $\lambda($ in $\AA)=\frac{12375}{W(e V)}$ comes from $W=\frac{h c}{\lambda}$
BETA
