Rankers Physics

Photoelectric Effects and deBroglie Equation: Practice Problem & Solution

The work functions for metals A, B and C are respectively 1.92 eV, 2.0 eV and 5 eV. According to Einstein's equation, the metals which will emit photoelectrons for a radiation of wavelength $4100 \mathring{A}$ is/are: (2005)
None
A only
A and B only
All the three metals

Solution Explained:

To solve this problem, we apply the core principles of Photoelectric Effects and deBroglie Equation. Understanding the underlying formula is key to arriving at the correct answer below:

The energy of the incident photon is $E = \frac{hc}{\lambda} = \frac{12400}{4100} eV \approx 3.02 eV$ . For photoelectric emission to occur, the incident energy must be greater than the work function ( $E > W$ ). Since $3.02 eV$ is greater than the work functions of A ( $1.92 eV$ ) and B ( $2.0 eV$ ) but less than C ( $5 eV$ ), only A and B will emit photoelectrons.

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