Determine the wavelength of the light absorbed when an electron in a hydrogen atom makes a transition from an orbital in which n = 2 to an orbital in which n =5

Respuesta :

The energy levels of the hydrogen atom are quantized and their energy is given by the approximated formula
[tex]E=- \frac{13.6}{n^2}[eV] [/tex]
where n is the number of the level.

In the transition from n=2 to n=5, the variation of energy is
[tex]\Delta E=E(n=5)-E(n=2)=-13.6 ( \frac{1}{5^2}- \frac{1}{2^2} )[eV]=2.86 eV[/tex]
Since this variation is positive, it means that the system has gained energy, so it must have absorbed a photon.

The energy of photon absorbed is equal to this [tex]\Delta E[/tex]. Converting it into Joule,
[tex]\Delta E=2.86 eV\cdot (1.6 \cdot 10^{-19})=4.57 \cdot 10^{-19} J[/tex]
The energy of the photon is
[tex]E=hf[/tex]
where h is the Planck constant while f is its frequency. Writing [tex]\Delta E=hf[/tex], we can write the frequency f of the photon:
[tex]f= \frac{\Delta E}{h}= \frac{4.57 \cdot 10^{-19} J}{6.62 \cdot 10^{-34}Js}=6.9 \cdot 10^{14}Hz [/tex]

The photon travels at the speed of light, [tex]c=3 \cdot 10^8 m/s[/tex], so its wavelength is
[tex]\lambda = \frac{c}{f}= \frac{3 \cdot 10^8 m/s}{6.9 \cdot 10^{14}Hz} =4.35 \cdot 10^{-7}m = 435 nm [/tex]


The wavelength of the light is about 4.34 × 10⁻⁷ m

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Further explanation

The term of package of electromagnetic wave radiation energy was first introduced by Max Planck. He termed it with photons with the magnitude is :

[tex]\large {\boxed {E = h \times f}}[/tex]

E = Energi of A Photon ( Joule )

h = Planck's Constant ( 6.63 × 10⁻³⁴ Js )

f = Frequency of Eletromagnetic Wave ( Hz )

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The photoelectric effect is an effect in which electrons are released from the metal surface when illuminated by electromagnetic waves with large enough of radiation energy.

[tex]\large {\boxed {E = \frac{1}{2}mv^2 + \Phi}}[/tex]

[tex]\large {\boxed {E = qV + \Phi}}[/tex]

E = Energi of A Photon ( Joule )

m = Mass of an Electron ( kg )

v = Electron Release Speed ( m/s )

Ф = Work Function of Metal ( Joule )

q = Charge of an Electron ( Coulomb )

V = Stopping Potential ( Volt )

Let us now tackle the problem !

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Given:

initial shell = n₁ = 2

final shell = n₂ = 5

Unknown:

ΔE = ?

Solution:

Firstly, we will use this following formula to calculate the change in energy of the electron:

[tex]\Delta E = R (\frac{1}{(n_2)^2} - \frac{1}{(n_1)^2})[/tex]

[tex]\Delta E = -2.18 \times 10^{-18} \times ( \frac{1}{5^2} - \frac{1}{2^2})[/tex]

[tex]\Delta E = -2.18 \times 10^{-18} \times ( \frac{1}{25} - \frac{1}{4} )[/tex]

[tex]\Delta E = -2.18 \times 10^{-18} \times (-\frac{21}{100})[/tex]

[tex]\boxed{\Delta E \approx 4.578 \times 10^{-19} \texttt{ J}}[/tex]

[tex]\texttt{ }[/tex]

Next, we will calculate the wavelength of the light:

[tex]\Delta E = h \frac{c}{\lambda}[/tex]

[tex]4.578 \times 10^{-19} = 6.63 \times 10^{-34} \times \frac{3 \times 10^8}{\lambda}[/tex]

[tex]\boxed{\lambda \approx 4.34 \times 10^{-7} \texttt{ m}}[/tex]

[tex]\texttt{ }[/tex]

Learn more

  • Photoelectric Effect : https://brainly.com/question/1408276
  • Statements about the Photoelectric Effect : https://brainly.com/question/9260704
  • Rutherford model and Photoelecric Effect : https://brainly.com/question/1458544

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Answer details

Grade: College

Subject: Physics

Chapter: Quantum Physics

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