NEET 2023 — Physics solution

NEET2023Physics

The work functions of Caesium (Cs), Potassium (K) and Sodium (Na) are $2.14$ eV, $2.30$ eV and $2.75$ eV respectively. If incident electromagnetic radiation has an incident energy of $2.20$ eV, which of these photosensitive surfaces may emit photoelectrons?

A
Both Na and K
B
K only
C
Na only
D
Cs only

Solution

Photoemission requires the incident photon energy to exceed the work function: $h ν > ϕ_{0}$ .

Incident energy $= 2.20$ eV. Comparing with $ϕ_{0}$ : Cs ( $2.14$ ) — emission possible; K ( $2.30$ ) — no; Na ( $2.75$ ) — no.

Only Cs emits photoelectrons.

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