Work function \((W_0)\) values of six metals (in eV) are given below: How many of the above metals do not eject electrons when they are struck with radiation of wavelength 400 nm?
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For photoelectric effect problems, compare photon energy \(E = \frac{hc}{\lambda}\) with the metal's work function \(W_0\). Electrons are emitted only if \(E \geq W_0\).
Step 1: Find photon energy at 400 nm. Use the shortcut: \(E = \frac{1240}{\lambda(\text{nm})}\) eV \(= \frac{1240}{400} = 3.1\) eV.
Step 2: Count metals with work function above 3.1 eV. Any metal whose work function \(W_0 > 3.1\) eV cannot eject electrons with this radiation. From the table, 3 metals satisfy this condition. \[ \boxed{3} \]
