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KVPY SX SB Exam 2012 Question Paper
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© examsnet.com
Question : 94
Total: 120
A stream of photons having energy 3 eV each impinges on a potassium surface. The work function of potassium is 2.3 eV. The emerging photo-electrons are slowed down by a copper plate placed 5 mm away. If the potential difference between the two metal plates is 1 V, the maximum distance the electrons can move away from the potassium surface before being turned back is
3.5 mm
1.5 mm
2.5 mm
5.0 mm
Validate
Solution:
K = 3 – 2.3 = 0.7eV ,
S
=
K
eE
and
E
=
V
d
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