Physics, 26.08.2020 22:01 NeemIsGreen

In the photoelectric effect, electrons are ejected from a metal surface when light strikes it. A certain minimum energy, Emin, is required to eject an electron. Any energy absorbed beyond that minimum gives kinetic energy to the electron. It is found that when light at a wavelength of 540 nm falls on a cesium surface, an electron is ejected with a kinetic energy of 260 x 10-20 1 When the wavelength is 400 nm, the kinetic energy is 1.54 x 10-19 J. (a) Calculate Emin for cesium in joules. (b) Calculate the longest wavelength, in nanometers, that will eject electrons from cesium.

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Answer from: aesthvx44

The minimum energy of the electron is $E_{min} = 34.2 \times 10^{(-20)} \;\rm J.$

The longest wavelength of the electron is 549 nm.

Given that, in the photoelectric effect, electrons are ejected from a metal surface when light strikes it. A certain minimum energy, Emin, is required to eject an electron. Also given wavelength of the light is 540 nm. The kinetic energy ejected by the electron is 260 x 10-20 J.

When the wavelength is 400 nm, the kinetic energy is 1.54 x 10-19 J.

The energy of the electron can be calculated as,

$E = hc/\lambda$

Where, is the energy of the electron, $h=6.626\times10^{(-34)} \;\rm Js$ is plank's constant, is the speed of light that is $3 \times 10^8 \;\rm m/s$ and $\lambda$ is the wavelength.

So the energy of the electron is,

$E = \dfrac{6.626\times 10^{(-34)} \times 3\times 10^8}{540\times 10^{(-9)}}$

$E = 3.68 \times 10^{(-19)} \;\rm J$

The energy of the electron is $E = 3.68 \times 10^{(-19)} \;\rm J$ .

The Emin can be calculated as given below.

$E_{min} = E - KE$

Where is the kinetic energy of the electron that is given as $260 \times 10^{(-20)} \;\rm J.$

So $E_{min} = 3.68\times 10^{(-19)} - 2.60\times 10^{(-20)}$

$E_{min} = 36.8\times 10^{(-20)} - 2.60\times 10^{(-20)}$

$E_{min} = 34.2 \times 10^{(-20)} \;\rm J.$

The minimum energy of the electron is $E_{min} = 34.2 \times 10^{(-20)} \;\rm J.$

For the longest wavelength, the electron will have its minimum energy that is Emin.

Hence, the longest wavelength can be calculated as given below.

$\lambda = \dfrac {h\times c} {E_{min}}$

$\lambda=\dfrac{6.626\times 10^{(-34)} \times 3\times 10^8} {34.2 \times 10^{(-20)}}$

$\lambda = 549 \times 10^{(-9)} \;\rm m\\\lambda = 549 \;\rm nm$

The longest wavelength of the electron is 549 nm.

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Answer from: allenpaietonp9v8sv

A) E_min = 36.21 × 10^(-20) J

B) 549 nm

Explanation:

A) The formula for energy of a photon is given as;

E = hc / λ

Where;

h is Planck's constant = 6.626 x 10^(-34) J.s

c is the speed of light = 3 × 10^(8) m/s

λ is wavelength

Wavelength is given as; 540 nm = 540 × 10^(-9) m

Thus;

E = (6.626 × 10^(-34) × 3 × 10^(8))/(540 × 10^(-9))

E = 36.81 × 10^(-20) J

We are given kinetic energy as;2.60 x 10^(-20) J

Now formula for E_min is;

E_min = E - K.E

E_min = (36.81 × 10^(-20)) - (2.60 x 10^(-20))

E_min = 36.21 × 10^(-20) J

B) the longest wavelength, in nanometers, that will eject electrons from cesium would have an energy that would be equal to E_min.

Thus,

36.21 × 10^(-20) = (6.626 × 10^(-34) × 3 × 10^(8))/λ

Making λ the subject gives;

λ = (6.626 × 10^(-34) × 3 × 10^(8))/36.21 × 10^(-20) = 549 x 10(-9) = 549 nm

Answer from: Quest

quantum mechanics or quantum physics is physics of very small objects (particles) and physical entities.

quantum physics has some parallels to our macro world and some pretty unique ideas which theoretically and mathematically proven to be true even though we will never be able to access them because of our size.

there are many types of particles: subatomic, elementary etc.

subatomic means they are smaller than atom, elementary means they are at the very basis of everything.

subatomic particles are for eg. protons, neutrons but not electrons.

elementary particles are categorised into 3 groups by what they do.

these 3 groups are quarks, leptons and bosons.

light for example is a particle more precisely a photon a part of leptons.

proton (subatomic particle) is made out of 2 up quarks and 1 down quark each of these has a fractional charge like $\frac{1}{3}$ . (i crazy)

most famous scientist who contributed to this physics are:

max planckalbert einsteinerwin schrödingermany

the topic itself us understand a lot and will probably be vastly used in the future (quantum computers, understanding the big bang,

we also must not forget quantum effects like:

superposition (where 1 thing can be this and that at the same time),entanglement (where two particles are seemingly connected by some sort of unknown (or known) force, energy, matter (i know all that can be the same at least it was at the beginning)

and there is more. but probably too much for this answer to be consistent due to my average understanding of this topic.

hope this you understand quantum mechanics a little more. i'm not an expert in the topic (so don't be like wth if you are an expert) but i'm very interested in it.

anyways quantum physics is a very hard topic (harder than physics (perhaps)) therefore searching for every information there is about it and learning it is unfortunately impossible (you can only specialise into 1 - 3 things or more (perhaps

have fun and i wish you luck!

r3t40

Answer from: Quest

spare some change and give it to the poor

explanation:

plz : ((

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