Lights of wavelengths λ 1 = 340 nm and λ 2 = 540 nm are incident on a metallic surface. If the ratio of the maximum speeds of the electrons ejected is 2 , the work function of the metal is

Question

Lights of wavelengths λ 1 = 340 nm and λ 2 = 540 nm are incident on a metallic surface. If the ratio of the maximum speeds of the electrons ejected is 2 , the work function of the metal is, 2 eV, 1.85 eV, 1 eV, 1.5 eV

MARKS App · Accepted Answer

λ 1 = 350 nm , λ 2 = 540 nm , V 1 V 2 = 2 ⇒ V 1 = 2 V and V 2 = V hc λ 1 = ϕ + 1 2 m ( 2 V ) 2 hc λ 2 = ϕ + 1 2 mV 2 hc λ 1 - hc λ 2 × 4 = ϕ - 4 ϕ hc ( 4 540 nm - 1 340 nm ) = 3 ϕ ϕ = 1.8 eV

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