Dual Nature Of Radiation And Matter Ques 77
77. Ultraviolet radiations of $6.2$ $ eV$ falls on an aluminium surface. $K.E.$ of fastest electron emitted is (work function $=4.2$ $ eV$ )
[1989]
(a) $3.2 \times 10^{-21} $ $J$
(b) $3.2 \times 10^{-19} $ $J$
(c) $7 \times 10^{-25} $ $J$
(d) $9 \times 10^{-32} $ $J$
Show Answer
Answer:
Correct Answer: 77.(b)
Solution:
- (b) K.E. of fastest electron $=E-W_0=6.2-4.2=2.0$ $ eV$
$=2 \times 1.6 \times 10^{-19}=3.2 \times 10^{-19} $ $J$
BETA
