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Solved problems for the chapter:

Photoelectric Effect

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Introduction to Light

1. Speed of light

2. Wavelength and frequency of light

3. Sources of light

3.1. Light sources based on black body radiation

3.2. Light emission due to changes in the energy levels of atoms

4. Luminous intensity and illuminance

5. Light perception

6. Forum

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Photons and Photoelectric Effect

1. Photons

1.1. Electron volts

2. Photoeffect or photoelectric effect

2.1. Dead current

3. Forum

↓ Show theory [2] ↓

Detailed solution steps are available at:

https://en.openprof.com/wb/chapter:photoelectric_effect/4539/

Example 1.

The energy of photons of light that shines on the surface of a gold piece is 9.2 eV. We measure the kinetic energy of the electrons coming from the illuminated surface to be 4.1 eV.

What is the work function of this gold piece?
What is the threshold wavelength at which we can still observe ejected electrons?

Note that:

Example 2.

The wavelength of visible light is between 380 nm (purple light) to 750 nm (red light).

What is the frequency band of visible light?
How many octaves does visible light cover?
Compare the result with the number of octaves of audible sound.

A metal is illuminated with light consisting of photons with an energy of 3.4 eV. The work function for an electron in this metal is 1.82 eV. Calculate the kinetic energy of the ejected electron.

Calculate the energy of a photon with a wavelength of 630 nm. Which part of the electromagnetic wave spectrum does this photon belong?

Photons of light with an energy of 3.09 eV strike a metal. The work function of this metal is 2.0 eV. Calculate the speed of the ejected electrons.

Note that:

The energy of the photon that hits a metal surface is 14.12 eV. After the ejection of an electron, we measure that the electron has a kinetic energy of What is the work function for this metal in eV?

Note that:

The work function of a calcium crystal is 2.9 eV. Calculate the energy of the photons of light with which we illuminate a piece of calcium and thereby obtain electrons with kinetic energy .

Note that:

The speed of the ejected electrons from a metal with a work function of 4.5 eV, is 950 km/s. Calculate the wavelength of light used to illuminate the given metal.

Note that:

The surface of a metal is illuminated with light photons of energy 14 eV. We manage to stop the electrons emerging from the metal with a stopping potential of 9.3 V. Calculate the work function of this metal.

Note that:

10.

A metal is illuminated with light photons and the exiting electrons are stopped with a stopping voltage of 9.3 V. Calculate the frequency of the light photons with which we illuminate the metal. The work function of an electron in this metal is 4.5 eV.

Note that:

11.

A metal is irradiated with light photons of a wavelength of 350 nm, and the emitted electrons from the metal are then stopped with a stopping potential of 2.04 V. If the same metal is irradiated with light photons of a wavelength of 450 nm, the emitted electrons are stopped with a stopping potential of 1.26 V. Calculate Planck's constant .

Note that:

12.

A laser with an average emitting power of 30 W emits light with a wavelength of 633 nm in pulses lasting 10 ns. What is the number of photons in one pulse?

Note that:

13.

Light of wavelength of 633 is shone on a metal. The work function of this metal is 4.7 eV. What is the kinetic energy of the ejected electrons?

Note that:

14.

A metal plate is illuminated with some light. We want the speed of the ejected electrons to be as high as possible. What we can do to achieve the desired goal?

We shorten the distance between the light source and the surface of the metal.
We reduce the wavelength of the light.
We increase the brightness of the source.
We increase the angle of incidence of the light on the metal.
We increase the frequency of the light.
We increase the power of the light source.
We reduce the angle of incidence of the light on the metal.
We increase the wavelength of the light.

15.

Which figure shows the correct graph of the relationship between the kinetic energy of the ejected electrons and the frequency of the incident photons in the photoelectric effect?

Graph of the kinetic energy of ejected eletrons against the frequency of incident light photons

16.

Luminous flux of 0.5 W falls on the surface of the light cell. The light is monochromatic with a wavelength of 496 nm. How much electric current does the cell produce if each photon ejects one electron?