Sodium and copper have work functions 2.3 eV and 4.5 eV respectively. Then the ratio of threshold wavelengths is nearest to :

1 : 2

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4 : 1

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2 : 1

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1 : 4

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Solution

The correct option is D $2 : 1$
Work function(W) $= \frac{h c}{λ}$
where, h = Planck's constant,
c = velocity of light

Therefore, $\frac{w_{n a}}{W_{c u}} = \frac{λ_{c u}}{λ_{n a}}$

$\frac{λ_{N a}}{λ_{c u}} = \frac{W_{c u}}{w_{n a}} = \frac{4.5}{2.3} =$ 2 (nearly)

So, the answer is option (C).

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Sodium and copper have work functions 2.3 eV and 4.5 eV respectively. Then the ratio of threshold wavelengths is nearest to :

The correct option is D 2:1Work function(W) =hcλwhere, h = Planck's constant,c = velocity of lightTherefore, wnaWcu=λcuλnaλNaλcu=Wcuwna=4.52.3= 2 (nearly)So, the answer is option (C).