The photoelectric threshold wavelength of silver is 3250 × 10 – 10 m . The velocity of the electron ejected…

The photoelectric threshold wavelength of silver is 3250×1010 m. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength 2536×1010 m is:-
Given h=4.14×10-15 eV s  and c=3×108 m s-1
  1. 6×106 m s-1
  2. 0.6×106 m s-1
  3. 61×103 m s-1
  4. 0.3×106 m s-1

Solution

λ0=3250×10-10 m
λ=2536×10-10  m
ϕ=hcλ0=1242 eV-nm325 nm=3.82 eV
hν=hcλ=1242 eV-nm253.6 nm=4.89 eV
By Einstein’s photoelectric equation
Kmax=hcλ- hc λ 0
KEmax=4.89-3.82 eV=1.07 eV
12mv2=1.07×1.6×10-19
v= 2×1.07×1.6×10-199.1×10-31
v=0.6×106 m/s

Asked in: NEET 2017

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