Question

What is the kinetic energy of the emitted electrons when cesium is exposed to UV rays of frequency 1.0×1015Hz?

Answer 1

The kinetic energy of the emitted electrons when cesium is exposed to UV rays of frequency 1.0x10^15Hz is 3.266x10^-19J.

Further explanation

Calculations

As   Energy=hf

E=6.626x10^-34 x 1.0x10^15

E=6.626x10^-19J

Since work function of cesium=2.1eV

And by converting its value in joule unit it will be

2.1eV=3.36x10^-19

KE of the emitted electrons=hf-(work function)

KE=6.626x10^-19J - 3.36x10^-19

KE=3.266x10^-19J

Explanation

The photon of light knocks out electrons from any metal surface. One photon emits one electron from metal surface. A photon must have enough energy to knock out electrons from a metal surface because if the energy of the incident photon will be less than the work function of metal surface than no electrons will be ejected from the metal surface. The kinetic energy of emitted electrons is the energy left after knocking out electron as some energy is used to knock out electrons. So the kinetic energy of emitted electrons is equal to the total energy of photon minus the work function of metal.  

Work function  

Work function is the minimum amount of energy required to eject an electron from a metal surface. The number of electrons which are emitted and their kinetic energy can be measured as function of frequency of light and its intensity. The kinetic energy of the emitted electrons is equal to the energy of the incident photon minus the work function of metal.  

Answer details

Subject: Chemistry

Level: College

Keywords

• Calculations
• Explanation
• Work function

Learn more to evaluate

brainly.com/question/11073849

brainly.com/question/10885719

Answer 2

The kinetic energy of the emitted electrons of cesium when it is exposed to UV rays of frequency $1.0 \times {10^{15}}\;{\text{Hz}}$  is  $\boxed{6.63 \times {{10}^{ - 19}}\;{\text{J}}}$

Further Explanation:

Photoelectric effect:

When light is made to fall on any substance, electrons are emitted from it. This is known as the photoelectric effect and the emitted electrons are called photoelectrons. The electrons are emitted because of the transference of energy from light to the electrons.

Cesium is a member of the alkali metal group so it is highly reactive and shows photoelectric effect to the maximum extent. It can remove its electron so easily because of its atomic size. Due to large atomic size of cesium, its outermost electrons are held very less tightly to the nucleus and therefore removed easily.

According to the Planck-Einstein equation, the energy is proportional to the frequency and is expressed as follows:

${\mathbf{E=h\nu }}$                                   ......(1)

Here,

${\text{E}}$ is the energy.

$h$ is the Plank’s constant.

$\nu$ is the frequency.

The frequency of UV rays is $1.0 \times {10^{15}}\;{\text{Hz}}$ or $1.0 \times {10^{15}}\;{{\text{s}}^{ - 1}}$

The value of Planck’s constant is $6.626 \times {10^{ - 34}}\;{\text{J}}\cdot{\text{s}}$ .

Substitute these values in equation (1)

$\begin{aligned}{\text{E}}&=\left( {6.626 \times {{10}^{ - 34}}\;{\text{J}}\cdot{\text{s}}}\right)\left( {1.0 \times {{10}^{15}}\;{{\text{s}}^{ - 1}}}\right)\\&=6.63\times {10^{ - 19}}\;{\text{J}}\\\end{aligned}$

But when electrons are ejected out from the surface of the substance, all of its energy is considered as kinetic energy.

So the kinetic energy of the electrons is ${\mathbf{6}}{\mathbf{.63 \times 1}}{{\mathbf{0}}^{{\mathbf{ - 19}}}}\;{\mathbf{J}}$ .

Learn more:

1. Statement about subatomic particle: brainly.com/question/3176193

2. The energy of a photon in light: brainly.com/question/7590814

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Structure of the atom

Keywords: kinetic energy, frequency, energy, photoelectric effect, Planck's constant, light, electrons, photoelectrons, proportional, transference, reactive, cesium.