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DedPeter [7]
3 years ago
9

If the work function of a material is such that red light of wavelength 700 nm just barely initiates the photoelectric effect, w

hat must the maximum kinetic energy of ejected electrons be when violet light of wavelength 400 nm illuminates the material?Express your answer with the appropriate units.Kmax = J
Physics
1 answer:
lawyer [7]3 years ago
7 0

Answer: 2.13(10)^{-19} J

Explanation:

The photoelectric effect consists of the emission of electrons (electric current) that occurs when light falls on a metal surface under certain conditions.  

If the light is a stream of photons and each of them has energy, this energy is able to pull an electron out of the crystalline lattice of the metal and communicate, in addition, a kinetic energy.  

<u>This is what Einstein proposed:  </u>

Light behaves like a stream of particles called photons with an energy  E

E=h.f (1)

Where:

h=6.63(10)^{-34}J.s is the Planck constant  

f is the frequency

Now, the frequency has an inverse relation with the wavelength \lambda:  

f=\frac{c}{\lambda} (2)  

Where c=3(10)^{8}m/s is the speed of light in vacuum  and \lambda=400nm=400(10)^{-9}m is the wavelength of the absorbed photons in the photoelectric effect.

Substituting (2) in (1):

E=\frac{h.c}{\lambda} (3)

So, the energy E of the incident photon must be equal to the sum of the Work function \Phi of the metal and the maximum kinetic energy K_{max} of the photoelectron:  

E=\Phi+K_{max} (4)  

Rewriting to find K_{max}:

K_{max}=E-\Phi (5)

Where \Phi is the minimum amount of energy required to induce the photoemission of electrons from the surface of a metal, and its value depends on the metal:

\Phi=h.f_{o}=\frac{h.c}{\lambda_{o}} (6)

Being \lambda_{o}=700nm=700(10)^{-9}m the threshold wavelength (the minimum wavelength needed to initiate the photoelectric effect)

Substituting (3) and (6) in (5):  

K_{max}=\frac{h.c}{\lambda}-\frac{h.c}{\lambda_{o}}

K_{max}=h.c(\frac{1}{\lambda}-\frac{1}{\lambda_{o}}) (7)

Substituting the known values:

K_{max}=(6.63(10)^{-34}J.s)(3(10)^{8}m/s)(\frac{1}{400(10)^{-9}m}-\frac{1}{700(10)^{-9}m})

K_{max}=2.13(10)^{-19} J >>>>>This is the maximum kinetic energy that ejected electrons must have when violet light illuminates the material

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ki77a [65]

Answer:

0.28802

2.57162 W

14.28 W

53.55 W

6.07142 W

Explanation:

R = 280Ω

L = 100 mH

C = 0.800 μF

V = 50 V

ω = 10500rad/s

For RLC circuit impedance is given by

Z=\sqrt{R^2+(X_L-X_C)^2}\\\Rightarrow Z=\sqrt{R^2+(\omega L-\dfrac{1}{\omega C})^2}\\\Rightarrow Z=\sqrt{280^2+(10500\times 100\times 10^{-3}-\dfrac{1}{10500\times 0.8\times 10^{-6}})^2}\\\Rightarrow Z=972.1483\ \Omega

Power factor is given by

F=\dfrac{R}{Z}\\\Rightarrow F=\dfrac{280}{972.1483}\\\Rightarrow F=0.28802

The power factor is 0.28802

The average power to the circuit is given by

P=\dfrac{V^2}{Z}\\\Rightarrow P=\dfrac{50^2}{972.1483}\\\Rightarrow P=2.57162\ W

The average power to the circuit is 2.57162 W

Power to resistor

P_R=IR\\\Rightarrow P_R=5.1\times 10^{-2}\times 280\\\Rightarrow P_R=14.28\ W

Power to resistor is 14.28 W

Power to inductor

P_L=IX_L\\\Rightarrow P_L=5.1\times 10^{-2}\times 10500\times 100\times 10^{-3}\\\Rightarrow P_L=53.55\ W

Power to the inductor is 53.55 W

Power to the capacitor

P_C=IX_C\\\Rightarrow P_C=5.1\times 10^{-2}\times \dfrac{1}{10500\times 0.8\times 10^{-6}}\\\Rightarrow P_C=6.07142\ W

The power to the capacitor is 6.07142 W

8 0
3 years ago
Wнιcн deмonѕтraтeѕ condυcтιon
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C.) cool feet walking across a hot pavement.



The reason because the other ones deals with radiation. Only C.) is the right answer because the feet is touching the hot pavement which is conduction. 
3 0
3 years ago
You have just been made the CEO (Chief Executive Officer) of a major company (like Amazon or Tesla). Now, you have the power to
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When I become a CEO (Chief Executive Officer) of a large company (like Amazon or Tesla), I would make the company more humane, with great parameters of working conditions, paying good salaries, so we would improve production and people would be happier , being an example to the whole world of a company that values and respects its employees.

<h3>Who is the CEO?</h3>

The CEO is essentially the highest-ranking executive in the company. He has most of the power. He reports directly to the board of directors. On the other hand, the president is below the CEO in the company hierarchy.

<h3>What does the CEO of a company do?</h3>

Direct the company's next steps through strategic planning; Take care, together with directors and shareholders of the company's health; Implement or modify processes within the company or sectors; Represent and relate to external audiences.

With this information, we can conclude that  I would make the company more humane, with great parameters of working conditions

Learn more about CEO in brainly.com/question/14747141

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5 0
1 year ago
Which of the following is a potential result of preparing appropriately before starting an experiment in a lab?
oksano4ka [1.4K]

Answer:

Your project goes well.

Explanation:

Because that's how it works.

6 0
3 years ago
HELP ASAP!!
Arada [10]
Percentage error:

1.55 – 1.53 ÷ 1.53
0.02 ÷ 1.53
.013 x 100
1.3 % error

I hope this is right.
7 0
3 years ago
Read 2 more answers
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