Niels Bohr developed his atomic theory in 1913 which proposed that electrons orbit the nucleus in fixed, quantized energy levels. The Bohr model could reproduce the emission spectrum of hydrogen and predict wavelengths of photons emitted during transitions between energy levels. While an oversimplification, the Bohr model was pioneering in introducing quantum mechanics and helped establish the modern understanding of atomic structure.
An entry in the 'schools for you' project. By Aneesh Bapat, class 8 from Abhinav Vidyalaya English Medium High School, Pune, India.About the various theories by different scientists about the structure of the atom.
An entry in the 'schools for you' project. By Aneesh Bapat, class 8 from Abhinav Vidyalaya English Medium High School, Pune, India.About the various theories by different scientists about the structure of the atom.
This is a powerpoint presentation that discusses about the topic or lesson: Dalton's Atomic Model. It also includes the history of John Dalton, characteristics and concepts of Dalton's Atomic Model.
4.1 The Atomic Models of Thomson and Rutherford
4.2 Rutherford Scattering
4.3 The Classic Atomic Model
4.4 The Bohr Model of the Hydrogen Atom
4.5 Successes and Failures of the Bohr Model
4.6 Characteristic X-Ray Spectra and Atomic Number
4.7 Atomic Excitation by Electrons
Bohr's Theory is based on an early model of atom where electrons travel round the nucleus in a discrete stable numbers of orbit determined by Quantum conditions. This is an extension of Rutherford Model of atom.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
2. Niels Bohr was born on October 7, 1885 and he died on
November 18, 1962. He was born in Copenhagen, Denmark
and he died in the same area. His parents were Christian Bohr
and Ellen Adler, (Bohr). He had an older sister named Jenny,
who was born in 1883, and a younger brother named Harald who
was born in 1887. Harald and Niels were very close through out
his childhood and he was often heard saying that Harald was his
best friend all through his life.
Niels entered the Grammelholms school in October of 1891, he
attended this school for his complete secondary education. He
did fairly well in school but could never lay claim to a brilliant mind,
he usually came in forth or fifth in a class of twenty. In his last two
years in school Niels specialized in mathematics and physics, he
frightened his math teacher with his exceptional skills and would
work ahead in the physics textbook often pointing out errors in
the text. He was learned more about this subject than he did from
his teachers.
Bohr entered the University of Copenhagen in 1903. Physics
was his major and he had minors in mathematics and chemistry.
3. When he was in University he wouldn’t have been able to carry out
any experiments in physics because the University didn’t have a
laboratory, so he used his father’s physiology lab. And his first paper
describes some of the experiments he did in the lab, he dedicated this
paper to his brother, Harald. Due to this paper, Bohr, won the Gold
Medal for 1906 from the Royal Danish Academy of Sciences, this
was for his analysis of water jets being used to determine surface
tension. He got his masters degree from the University of
Copenhagen in 1909, and his doctorate in 1911for his thesis,
Studies on the electron theory of metals. This thesis was dedicated
to his father, who had died earlier in the year from a heart attack Bohr
was engaged to Margrethe Norlund, who, many say, placed a key role
in his successfulness, at the time of his father’s death.
In 1911 in the month of September Bohr went to England to study
with J J Thompson at Cambridge, he had hoped to spend a long
period of time with Thompson, but, unfortunately, they didn’t get
along. Lucky for him, he had met Rutherford earlier in that year and
went to study with him instead, this was right after Rutherford had
published his theory, which states that the bulk of the mass of an atom
can be found in the nucleus.
4. Bohr began developing his theory in June of 1912 He did his fundamental
work on the hydrogen atom eventually he even did some work on some
heavier atoms. Bohr returned to Copenhagen to continue working on his
theory which he completed to his satisfaction in and around July of 1913.
The University recommended his name for a chair in theoretical physics,
he expected his position to be confirmed within a year. It wasn’t to be. He
spent the next four years working with Rutherford and his group yet again,
he enjoyed his time with the group immensely, participating in many break
through activities.
His completed theory of the atom gave us the clue as to where, exactly,
electrons were found in an atom. He stated that electrons traveled on fixed
energy levels. Sort of like a ladder, these electrons could change orbits
but they would always be found in an orbit and there would always be a
certain number of electrons in the orbital.
5. Changing Energy Levels
The fact that there were certain orbits and energies in an atom was part of
Bohr’s theory. When these energies change levels there is a different color
given off.
11. Emission spectrum of H
We can use the emission spectrum to determine the
energy levels forthe hydrogen atom.
12. Balmer Model
• Joseph Balmer (1885) first noticed that the
frequency of visiblelinesin theH atom spectrum
could bereproduced by:
ν∝
1
22
−
1
n2
n = 3, 4, 5, …..
• Theaboveequation predictsthat asn increases,
thefrequenciesbecomemoreclosely spaced.
13. Rydberg Model
• Johann Rydberg extendstheBalmer model by
finding moreemission linesoutsidethevisible
region of thespectrum:
ν=Ry
1
n1
2
−
1
n2
2
n1 = 1, 2, 3, …..
• Thissuggeststhat theenergy levelsof theH atom
areproportional to 1/n2
n2 = n1+1, n1+2, …
Ry = 3.29 x 1015
1/s
14. The Bohr
Model
• NielsBohr usestheemission spectrum of
hydrogen to develop aquantum model for H.
• Central idea: electron circlesthe“nucleus” in
only certain allowed circular orbitals.
• Bohr postulatesthat thereisCoulombic attraction
between e- and nucleus. However, classical
physicsisunableto explain why an H atom
doesn’t simply collapse.
15. The Bohr Model (cont.)
• Bohr model for theH atom iscapableof
reproducing theenergy levelsgiven by the
empirical formulasof Balmer and Rydberg.
E=−2.178x10−18
J
Z2
n2
Z = atomic number (1 for H)
n = integer (1, 2, ….)
• Ry x h = -2.178 x 10-18
J(!)
16. The Bohr Model (cont.)
E=−2.178x10−18
J
Z2
n2
• Energy levelsget closer together
asn increases
• at n = infinity, E = 0
17. The Bohr Model (cont.)
• Wecan usetheBohr model to predict what DE is
for any two energy levels
∆E=Efinal−Einitial
∆E=−2.178x10−18
J
1
nfinal
2
−(−2.178x10−18
J)
1
ninitial
2
∆E=−2.178x10−18
J
1
nfinal
2
−
1
ninitial
2
18. The Bohr Model (cont.)
• Example: At what wavelength will emission from
n = 4 to n = 1 for theH atom beobserved?
∆E=−2.178x10−18
J
1
nfinal
2
−
1
ninitial
2
1 4
∆E=−2.178x10−18
J1−
1
16
=−2.04x10−18
J
∆E=2.04x10−18
J=
hc
λ
λ=9.74x10−8
m=97.4nm
19. The Bohr Model (cont.)
• Example: What isthelongest wavelength of light
that will result in removal of thee-
from H?
∆E=−2.178x10−18
J
1
nfinal
2
−
1
ninitial
2
∞ 1
∆E=−2.178x10−18
J0−1( )=2.178x10−18
J
∆E=2.178x10−18
J=
hc
λ
λ=9.13x10−8
m=91.3nm
20. Extension to Higher Z
• TheBohr model can beextended to any single
electron system….must keep track of Z
(atomic number).
• Examples: He+
(Z = 2), Li+2
(Z = 3), etc.
E=−2.178x10−18
J
Z2
n2
Z = atomic number
n = integer (1, 2, ….)
21. Extension to Higher Z
(cont.)
• Example: At what wavelength will emission from
n = 4 to n = 1 for theHe+
atom beobserved?
∆E=−2.178x10−18
JZ2
( )
1
nfinal
2
−
1
ninitial
2
2
1 4
∆E=−2.178x10−18
J4()1−
1
16
=−8.16x10−18
J
∆E=8.16x10−18
J=
hc
λ
λ=2.43x10−8
m=24.3nm
λH>λHe+
22. Where does
this go
wrong?
• TheBohr model’ssuccessesarelimited:
• Doesn’t work for multi-electron atoms.
• The“electron racetrack” pictureisincorrect.
• That said, theBohr model wasapioneering,
“quantized” pictureof atomic energy levels.
