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Chapter 19: Problem 7

Two electrons of kinetic energy \(2.5 \mathrm{eV}\) fall on a metal plate, which has work function of \(4.0 \mathrm{eV}\). Number of electrons ejected from the metal surface is (A) One (B) Two (C) Zero (D) More than two

Short Answer

Expert verified
The number of electrons ejected from the metal surface is zero (Option C).

Step by step solution

01

Understanding the theory

Firstly, the theory behind the phenomenon must be understood. The photoelectric effect is the emission of electrons or other free carriers when light shines on a material. The work function of a metal is the minimum amount of energy that an electron requires to leave the metal surface. In this case, the work function of the material is given to be 4.0 eV.
02

Comparing the kinetic energy of the electrons and the work function

It's seen that each electron that hits the metal surface has a kinetic energy of 2.5 eV. This kinetic energy is less than the work function of the surface (4.0 eV). Hence, the incident electrons do not have enough energy to break free from the surface of the metal.
03

Final conclusion

Since the kinetic energy of the falling electrons (2.5 eV) is less than the work function of the metal plate (4.0 eV), the electrons do not have the required energy to overcome the work function and get ejected. Thus, the number of electrons ejected from the metal surface is zero.

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Most popular questions from this chapter

The 'rad' is the correct unit used to report the measurement of (A) the rate of decay of radioactive source. (B) the ability of a beam of gamma ray photons to produce ions in a target. (C) the energy delivered by radiation to a target. (D) the biological effect of radiation.

Radiation wavelength \(\lambda\), is incident on a photocell. The fastest emitted electron has speed \(v\). If the wavelength is changed to \(\frac{3 \lambda}{4}\), the speed of the fastest emitted electron will be: \((\mathrm{A})v\left(\frac{4}{3}\right)^{1 / 2}\)

When a certain metallic surface is illuminated with monochromatic light of wavelength \(\lambda\), the stopping potential for photoelectric current is \(3 V_{0}\). When the same surface is illuminated with the light of wavelength \(2 \lambda\), the stopping potential is \(V_{0}\). The threshold wavelength for the surface for photoelectric effect is (A) \(\frac{4 \lambda}{3}\) (B) \(4 \lambda\) (C) \(6 \lambda\) (D) \(8 \lambda\)

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The work function of aluminium is \(4.2 \mathrm{eV}\). If two photons, each of energy \(3.5 \mathrm{eV}\) strike an electron of aluminium, then emission of electrons will be (A) Possible. (B) Not possible. (C) Data is incomplete. (D) Depend upon the density of the surface.
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