Electrons with a maximum kinetic energy of 2.3 eV are ejected from a surface by ultraviolet phot

Electrons with a maximum kinetic energy of 2.3 eV are...

Key Concepts

Energy Unit Conversion

In physics, energy is often expressed in both joules and electron volts (eV), and converting between these units is essential for calculations involving quantum phenomena. Recognizing that one electron volt corresponds to approximately 1.602 × 10?¹? joules allows for consistent and accurate comparisons between the energy of photons, the kinetic energy of electrons, and the work function of materials.

Work Function

The work function is the minimum energy required to remove an electron from the surface of a material. It represents a threshold value below which no electron emission occurs, regardless of the number of incident photons, and it plays a crucial role in the photoelectric effect by determining the cutoff frequency or wavelength of the incident light.

Photoelectric Effect

The photoelectric effect describes the phenomenon in which electrons are ejected from a material's surface when light of sufficient energy strikes it. The maximum kinetic energy of the emitted electrons is given by the difference between the photon energy and the material’s work function, making this concept central to understanding quantum interactions between light and matter.

Photon Energy Calculation

This concept involves computing the energy of a photon using the relation E = hc/?, where h is Planck’s constant, c is the speed of light, and ? is the wavelength. This calculation is fundamental in quantifying how much energy is available from a photon, which can then be compared to the energy thresholds necessary for various physical processes such as electron emission.

Transcript

00:02 Hello, so the question is taken from electrons and photoelectric effect that is a part of this is a part of modern physics and the question is electrons with maximum kinetic energy so given that kinetic energy maximum is equal to 2 .3 electron world okay ejected for my surface by ultraviolet photons of wavelength so given that wavelength or violet photons are 200 micrometer.

00:38 Calculate the energy of incident photons in june.

00:41 So we need to evaluate here.

00:44 Incident energy of photons and second thing is smallest energy which can free an electron form metal surface.

00:53 So that smallest energy which is required to escape just electron for metal surface is known as work function.

01:02 So we need to evaluate this work.

01:04 Function and third is the wavelength of a photon with this energy and wavelength is called as threshold wavelength.

01:12 We need to evaluate these three values.

01:14 We know that we can write incident energy is equal to hc by lambda by planx hypothesis where h is the planx constant c is the velocity of lighting, lambda is the wavelength of incident photon.

01:31 So the value of planx constant is 6 .62 into 10 to the power minus 34 jule second.

01:38 Velocity of light is 3 into 10 to the power 8 meter per second and wavelength is already given.

01:44 That is 200 micrometer.

01:47 Micro is 10 to the power minus 6.

01:49 So from here, incident energy is equal to.

01:57 So let me evaluate that value.

02:03 I think that is not 200 micrometer.

02:07 That must be 200 nanometer because the ultraviolet photons having wavelength i think that is yes that is 200 nanometer so that will be 200 into 10 to the power minus 9 otherwise they are not lying in that range okay so let me evaluate this incident energy in this will give us the value of energy incident energy in jule basically the ultraviolet photon lies after the visible range and visible light is having range between 4 000 to 7 000 nanometer and and the ultraviolet photons having energy slightly higher than that of the visible light so that must lie that must have energy more than that of the visible light so this is the main reason why i'm taking it 200 into 10 to the power minus 9.

03:09 Because if we take 200 into 10 to the power minus 6, that lie, that are having more energy.

03:15 Okay, so that is why i'm writing it as 200 nanometer.

03:20 So let me evaluate that value...

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