Photoelectric Effect Problems And Solutions Pdf

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These solutions for Photoelectric Effect And Wave—particle Duality are extremely popular among Class 11 Science students for Physics Photoelectric Effect And Wave—particle Duality Solutions come handy for quickly completing your homework and preparing for exams. A photon has zero rest mass.

Around the turn of the twentieth century, it was observed by a number of physicists including Hertz, Thomson and Von Lenard that when light was shone onto a metal plate, electrons were emitted by the metal. This is called the photoelectric effect. The characteristics of the photoelectric effect were a surprise and a very important development in modern Physics. To understand why it was a surprise we need to look at the history to understand what physicists were expecting to happen and then understand the implications for Physics going forward.

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Chapter Particles and Waves :. In this chapter, the particle-like behavior of light will be discussed. In fact, the particle-like behavior is also associated with a frequency and it cannot be separated form the wave-like behavior Quantum Optics.

When an electron receives extra energy, it then has to change its orbit or radius of rotation. It has to take an orbit of greater radius. The radius it takes is not just any radius. The radii of rotation for any electron orbiting a nucleus are discrete values that will be discussed in the chapter on atomic physics. When such transition occurs, a vacant orbit is left behind that must be filled. It may be filled by the same electron or any other one. The electron that fills that vacant orbit must have the correct energy that matches the energy of that orbit.

The electron that fills that orbit may have excess energy that has to be given off before being able to fill that vacant orbit. The excess energy is simply the energy difference between two different orbits.

The Plancks' formula is :. Our answer is a little more than 1eV. In fact it is 2. This photon is not in the visible range. The Photoelectric Effect :. The mechanism by which photoelectric effec t operates may be used to verify the particle-like behavior of light. A photoelectric cell can be made of a vacuum tube in which two metallic plates or poles are fixed. The two plates are connected to two wires that come out of the sealed glass tube and are used for connection to other electronic components.

For time being, let us connect a photoelectric cell to just a galvanometer sensitive ammeter as shown in the figure below. Each energetic photon that collides with the metal surface, releases one electron.

This released electron has some speed and therefore some K. The atoms of the outer surface that have lost electrons, replenish their electron deficiencies from the inner layer atoms of the metal oxide or the nearby free electrons. This replenishing process transmits layer by layer through the wire and the galvanometer all the way to the pole labeled "Positive. The positive end pulls the released electrons from the negative end through the vacuum tube and the circuit completes itself.

This process occurs very fast. As soon as light hits the metal plate, the circuit is on. As soon as light is cut off, the circuit goes off. The conclusion of the above experiment is that photons of light act as particles and kick electrons out of their orbit. This verifies the particle-like behavior of light.

The Photoelectric Cell Formula:. There is a limit for frequency below which nothing happens. That limit happens when the frequency of the incident photon is just enough to release an electron.

Such released electron has a K. At the limiting frequency called the " threshold frequency ", the K. With K. The wavelength of the incident photons is nm. Find a the frequency of the photons, b the K. Wave-Particle Duality :. Chapter 29 Test Yourself Each released electron has an energy of a 4. The wavelength of the incident photons on it is nm. Find a the frequency of the photons, b the energy of each, c the K. When the light is cut off, the current stops. This shows that the collision of photons of light on the metal surface must release electrons from the outer shells of the outermost atomic layers of the metallic plate.

Photoelectric effect – problems and solutions

Calculate the range of energy of the photons of visible light. Find the net energy absorbed by the atom in the process. Calculate the force exerted by the light beam on the mirror. Find the power of the source needed to support the weight of the mirror. Thus it exerts force. Find the pressure exerted by the light on the surface of the chamber. If the sphere completely absorbs the radiation falling on it, find the force exerted by the light beam on the sphere.

When a metal surface is exposed to a monochromatic electromagnetic wave of sufficiently short wavelength or equivalently, above a threshold frequency , the incident radiation is absorbed and the exposed surface emits electrons. This phenomenon is known as the photoelectric effect. Electrons that are emitted in this process are called photoelectrons. The target material serves as the anode, which becomes the emitter of photoelectrons when it is illuminated by monochromatic radiation. We call this electrode the photoelectrode. Photoelectrons are collected at the cathode, which is kept at a lower potential with respect to the anode. The potential difference between the electrodes can be increased or decreased, or its polarity can be reversed.

What is the energy of each photon for the wavelengths and frequencies shown? Give answers in both Joules and electron-volts. Which of these photons is most likely to produce a current in the photoelectric effect? The 5. Comparing their energy to the work functions shown in the table above they would produce a current for sodium, copper, calcium, and gold, but not for gold. The red light would only produce a current if the target material had a very small work function. Microwaves and radiowaves have much too long a wavelength and too small a photon energy to eject any electrons.

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Around the turn of the twentieth century, it was observed by a number of physicists including Hertz, Thomson and Von Lenard that when light was shone onto a metal plate, electrons were emitted by the metal. This is called the photoelectric effect. The characteristics of the photoelectric effect were a surprise and a very important development in modern Physics. To understand why it was a surprise we need to look at the history to understand what physicists were expecting to happen and then understand the implications for Physics going forward. In , Heinrich Hertz a German physicist noticed that ultraviolet light incident on a metal plate could cause sparks.

Furthermore, emission takes place as soon as the light shines on the surface; there is no detectable delay. A major contribution to the subject was made by Niels Bohr of Denmark, who applied the quantum hypothesis to atomic spectra in The spectra of light emitted by gaseous atoms had been studied extensively since the midth century.

When a radiation is passed on to the surface of a metal, some amount of energy is used in overcoming the attraction force on the electron and knocks it out from the atom.

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The correct statement about the photoelectric effect is …. Can be explained by considering light as a wave. Electrons released by the metal surface will decrease if the light frequency increased. The intensity of light does not affect the energy of electrons coming out of the metal surface. The photoelectric effect occurs in the infrared region. The photoelectric effect will occur when the light intensity of the metal is large.

Photoelectric Effect The phenomenon of emission of photoelectron from the surface of metal, when a light beam of suitable frequency is incident on it, is called photoelectric effect. The emitted electrons are called photoelectrons and the current so produced is called photoelectric current. In his experimental investigation on the production of electromagnetic waves by means of spark across the detector loop were enhanced when the emitter plate was illuminated by ultraviolet light from an arc lamp. As soon as, the ultraviolet radiations were stopped, the current flows also stopped. These observations indicate that when ultraviolet radiations fall on the emitter plate, electrons are ejected from it which are attracted towards the positive plate by the electric field.


Example Problem: Photoelectric Effect. Physics TA: Brian Clark. 11/30/​ 1. A piece of metal has a cutoff wavelength of λcutoff = nm. Consider.


Chapter Particles and Waves :. In this chapter, the particle-like behavior of light will be discussed. In fact, the particle-like behavior is also associated with a frequency and it cannot be separated form the wave-like behavior Quantum Optics. When an electron receives extra energy, it then has to change its orbit or radius of rotation.

Around the turn of the twentieth century, it was observed by a number of physicists including Hertz, Thomson and Von Lenard that when light was shone onto a metal plate, electrons were emitted by the metal. This is called the photoelectric effect. The characteristics of the photoelectric effect were a surprise and a very important development in modern Physics. To understand why it was a surprise we need to look at the history to understand what physicists were expecting to happen and then understand the implications for Physics going forward.

Around the turn of the twentieth century, it was observed by a number of physicists including Hertz, Thomson and Von Lenard that when light was shone onto a metal plate, electrons were emitted by the metal. This is called the photoelectric effect. The characteristics of the photoelectric effect were a surprise and a very important development in modern Physics. To understand why it was a surprise we need to look at the history to understand what physicists were expecting to happen and then understand the implications for Physics going forward.

Photoelectric effect – problems and solutions

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