A clean nickel surface is exposed to light of wavelength 206 nm . What is the maximum speed of t

A clean nickel surface is exposed to light of wavelength 206...

Key Concepts

Photoelectric Effect

The photoelectric effect is the phenomenon in which electrons are emitted from a material when it is exposed to light of sufficiently high frequency. It demonstrates the particle nature of light and the quantization of energy, as the energy of each photon must exceed a certain threshold to eject an electron from the material's surface.

Work Function

The work function is the minimum energy required to remove an electron from the surface of a material. It is a characteristic property of each material and plays a crucial role in determining whether incident photons have enough energy to cause electron emission in the photoelectric effect.

Photon Energy

Photon energy refers to the energy carried by a single photon and is directly related to its wavelength by the equation E = hc/?, where h is Planck’s constant and c is the speed of light. This concept is fundamental in understanding how light can transfer energy to electrons in a material.

Kinetic Energy of Emitted Electrons

Once a photon provides sufficient energy to overcome the work function, any additional energy is converted into the kinetic energy of the emitted electron. This relationship is described by the equation KE = E_photon - Work Function, and allows for the calculation of the maximum speed of the photoelectrons using classical kinetic energy relations.

Transcript

00:01 So a few words about the photoelectric effect, which is an effect that demonstrates that light behaves like little quanta of packets of energy.

00:13 And the explanation of this phenomena can only be made if light behaves as quanta of energy.

00:23 But the idea is, or the experiment involves the interaction of photons with either a metal surface or, a metal oxide.

00:34 A photon comes in and it must have enough energy so that it pulls the electron inside the surface out of the surface and perhaps gives the electron a little bit of energy once it leaves the surface.

00:50 So here is kind of a more energy level picture of what's going on.

00:54 The electron is in a potential well.

00:58 The depth of that well is known as the work function so when the photon gets absorbed, here's the electron, in comes the photon.

01:17 If it has enough energy to pull the electron out, the electron will come up to a potential energy of zero and leave the well with kinetic energy.

01:31 So the energy of the incoming photon goes to two things.

01:35 It goes into the potential energy, which, depending on the units of the work function, it could just be equal to the work function in electron volts.

01:48 Sometimes the work function is just given in volts, but the potential energy is the work function in electron volts.

01:58 And so the energy of the photon gets absorbed and brings the electron up to potential, equals to zero and then adds to the kinetic energy of the electron.

02:18 Meanwhile the photon disappears, gets totally absorbed.

02:23 Conservation of energy.

02:25 So let's take a look at an example.

02:27 We're going to take a nickel, clean nickel surface, so not a nickel oxide.

02:34 We can look up the work function.

02:36 It is 5 .1 electron bolts.

02:39 The energy of the photon coming in can be determined from hc over the wavelength, and we'll take the wavelength as a short ultraviolet to 106 nanometers...

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