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Physics - Modern Physics Question with Solution | TestHub

PhysicsModern PhysicsPhotoelectric effectMedium2 minQB

PhysicsMediumsingle choice

A hydrogen atom prepared in $n = 5$ decays via all possible spontaneous paths (so every allowed down transition that can occur in some cascade is counted as a potential emission line). These photons illuminate a metal with threshold wavelength $λ_{0} = 400 nm$ . How many distinct emitted lines can cause photoemission?

Options:

Answer:

Solution:

Threshold energy $E_{0} = \frac{1240}{400} = 3.1 eV$

From $n \leq 5$ , the only transitions with $E > 3.10 eV$ are : $n = 2 \to 1 (10.2 eV), n = 3 \to 1 (12.09 eV), n = 4 \to 1 (12.75 eV), n = 5 \to 1 (13.06 eV)$

Count = 4 hence (C).

Stream:JEESubject:PhysicsTopic:Modern PhysicsSubtopic:Photoelectric effect

⏱ 2mℹ️ Source: QB

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