Here, the vertical axis represents the energy of an electron, and the horizontal axis represents the frequency.Īfter frequency f o Hz, the kinetic energy of electrons start increasing proportionally with frequency.īelow, frequency f o or below energy hf o there will be no kinetic energy i.e. Now, If we graphically represent the above points we will get the graph below, Graphical Representation of Work Function The value of threshold frequency is different for different metals.
The frequency of incident light below which no photoemission on a metal surface gets initiated is called threshold frequency for that metal. But below this minimum frequency, there will be no kinetic energy in the electrons. Above this frequency, the kinetic energy of the emitted electron is directly proportional to incident light frequency. Hence after a certain minimum frequency of incident light, the electrons start emitted from a metal surface. Obviously, the number of photons strike on the metal surface increases hence more emitted electrons will be produced, but the kinetic energy of each electron will be unchanged as the frequency of incident light is fixed, in that case. But when an intensity of incident light gets increased without changing its frequency. Not on the intensity (Brightness of the light). Hence, how fast the electron will be emitted from the surface of the metal depends upon the frequency of incident light. If the frequency of light is higher than that above-mentioned minimum frequency, the extra energy of photon will be converted to kinetic energy of the emitted electron. Hence, for photoemission minimum frequency of incident light is required. Hence, the frequency is only variable upon which energy of photon rather light depends., It is found that there is no photoemission from a metal surface below a certain frequency of light. As the energy of one photon E photon = hf, the energy of each photon depends upon the frequency of light. This phenomenon is classically termed as photoemission. Now when the light strikes on a metal surface electrons on the surface of the metal get energy from the light and get emitted from the surface. Where h is Planck Constant and f is the frequency of light. The energy contained in each photon is hf. Sir Albert Einstein said that light is in the form of a beam of a huge number of discrete energy packets called photons. For that, we first have to know some basic features. You will understand more of the physics in this interesting article after you finish reading Angular Momentum.Work function can also be explained and defined by quantum physics. The work-energy theorem implies that a smaller change in kinetic energy results in a smaller penetration. The reason is that if the bullet hits off-center, it has a little kinetic energy after it stops penetrating, because the block rotates. If the bullet is fired dead center into the block, it loses all its kinetic energy and penetrates slightly farther than if fired off-center. The penetration of a bullet, fired vertically upward into a block of wood, is discussed in one section of Asif Shakur’s recent article. We could have used Newton’s second law and kinematics in this example, but the work-energy theorem also supplies an answer to less simple situations. Let’s start by looking at the net work done on a particle as it moves over an infinitesimal displacement, which is the dot product of the net force and the displacement: d Significance Therefore, we should consider the work done by all the forces acting on a particle, or the net work, to see what effect it has on the particle’s motion. We have discussed how to find the work done on a particle by the forces that act on it, but how is that work manifested in the motion of the particle? According to Newton’s second law of motion, the sum of all the forces acting on a particle, or the net force, determines the rate of change in the momentum of the particle, or its motion.
Use the work-energy theorem to find information about the forces acting on a particle, given information about its motion. Apply the work-energy theorem to find information about the motion of a particle, given the forces acting on it. By the end of this section, you will be able to:
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