Ultraviolet light of wavelength λ=200nm is used in an experiment on photoelectric effect with cesium (ϕ=1.8). Find De-Broglie wavelength of photo electron with maximum kinetic energy.
A
47×10−9m
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B
285×10−9m
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C
197×10−9m
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D
27×10−9m
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Solution
The correct option is A47×10−9m KEmax=hv−ϕ hν=1242200=6.21eV ϕ=1.8eV KEmax=6.21−1.8=4.41 =4.41eV λ=1.2√4.41nm=1.22.1nm=47×10−9m