Dual Nature of Radiation and Matter - Result Question 75
79. 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) $9 \times 10^{-32} J$
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Answer:
Correct Answer: 79. (b)
Solution:
- (b) K.E. of fastest electron $=E-W_0=6.2-4.2=2.0 eV$ $=2 \times 1.6 \times 10^{-19}=3.2 \times 10^{-19} J$
