Photoelectric Effect -05- Photoelectron Velocity

Rebiaz Studio

If the work function of a metal is 2.1 eV, if a photon with a wavelength of 5x10⁻⁷ m is incident on the metal surface, what is the maximum velocity of the electrons emitted?  Watch videos related to MODERN PHYSICS: https://dailymotion.com/playlist/x90qrm

Transcript

00:00Hi friends, don't let your fear hinder your learning.

00:07A metal plate has a specific work function.

00:12When photons with a frequency exceeding the threshold frequency are exposed to that surface,

00:17what is the speed of the photoelectrons?

00:20This worksheet lists the work function, photon wavelength, electron mass, electron charge,

00:27speed of light, and Planck's constant.

00:30There are many values, it turns out.

00:36Without further ado, let's discuss them.

00:40Before going any further, just write down some of the quantities shown on the worksheet.

00:47Of all these quantities, it seems only the work function uses non-international units.

00:54Electron volts can be converted to joules by multiplying that value by the electron charge.

01:00Now, we will analyze the metal plate.

01:07On the surface of this metal there are several free electrons.

01:10When exposed to light with a frequency exceeding the threshold frequency,

01:17these electrons are released from the electron cloud, moving in a straight line at a certain speed.

01:22Now, we are asked to find the value of this speed.

01:30Without dissipation, energy in physical processes is conserved.

01:34The energy after an electron is excited is equal to the energy before it is excited.

01:44Before it is excited, there is the photon energy and the electron binding energy.

01:48The binding energy is negative.

01:55That's why electrons always remain in the electron cloud.

02:01Once excited, they only have kinetic energy.

02:04Half of the squared V is equal to HF minus phi.

02:13Unfortunately, the question paper doesn't mention the frequency of the photon.

02:19Simply put, frequency is the speed of light divided by the wavelength.

02:23It seems like some of those values are already available.

02:33If the numbers are like this, we'll need to use a scientific calculator.

02:38From here, V squared is equal to 1.35 times 10 to the power of 11.

02:44V itself is 3.68 times 10 to the power of 5 meters per second.

02:52This is the speed of the photoelectron.

02:56The average speed of elementary particles is indeed very fast.

03:03Happy learning, everyone.

Category

Transcript

Be the first to comment

Recommended