This document discusses the dual nature of matter and radiation. It describes photons and their properties, as well as the photoelectric effect. Key laws of the photoelectric effect are provided, including Einstein's photoelectric equation. Experimental setups for studying the photoelectric effect are described. The document also discusses how the photoelectric effect provided evidence for the particle nature of light and radiation. Finally, it introduces the idea that matter also exhibits wave-particle duality based on de Broglie's hypothesis.
Understand the the phenomenon of Photoelectric effect with the help of virtual lab and also learn about the conditions required for this phenomenon.
Plot the graph between the observed quantities during performing this experiment.
And calculate the value of Planck's Constant ,work function and cut-off frequency with the help of Graph.
Understand the the phenomenon of Photoelectric effect with the help of virtual lab and also learn about the conditions required for this phenomenon.
Plot the graph between the observed quantities during performing this experiment.
And calculate the value of Planck's Constant ,work function and cut-off frequency with the help of Graph.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
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.
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.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
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SOCIAL SCIENCE
XII
MATRICULATION
UNIT NO 8
DUAL NATURE OF MATTER AND
RADIATIONS
● MATTER
● RADIATIONS
PHYSICS
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DUAL NATURE OF MATTER AND RADIATIONS
1. Photons
2. Photoelectric Effect
3. Experimental Set-up to study Photoelectric Effect
4. Effect of Intensity, Frequency, Potential on P.E. Current
5. Graphical representation of variation of P.E. Current
6. Laws of Photoelectric Effect
7. Einstein’s Photoelectric Equation
8. Verification of Laws of Photoelectric Effect based on Einstein’s
Photoelectric Equation
9. Application of Photoelectric Effect
10. Matter Waves and de Broglie wavelength
11. Davission & Germer Experiment
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Photon:
A packet or bundle of energy is called a photon.
Energy of a photon is E = hν =
hc
λ
where h is the Planck’s constant, ν is the frequency of the radiation or
photon, c is the speed of light (e.m. wave) and λ is the wavelength.
Properties of photons:
i) A photon travels at a speed of light c in vacuum. (i.e. 3 x 10-8 m/s)
ii) It has zero rest mass. i.e. the photon can not exist at rest.
iii) The kinetic mass of a photon is, m =
h
cλ
E
c2
=
iv) The momentum of a photon is, p =
h
λ
E
c
=
v) Photons travel in a straight line.
vi) Energy of a photon depends upon frequency of the photon; so the energy of the photon
does not change when photon travels from one medium to another.
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vii) Wavelength of the photon changes in different media; so, velocity of a photon
is different in different media.
viii) Photons are electrically neutral.
ix) Photons may show diffraction under given conditions.
x) Photons are not deviated by magnetic and electric fields.
Photoelectric Effect:
The phenomenon of emission of electrons from mainly metal surfaces exposed to light
energy (X – rays, γ – rays, UV rays, Visible light and even Infra Red rays) of suitable
frequency is known as photoelectric effect.
The electrons emitted by this effect are called photoelectrons. The current
constituted by photoelectrons is known as photoelectric current.
Note: Non metals also show photoelectric effect. Liquids and gases also show this
effect but to limited extent.
UV
Metals Metals other than Alkali Metals Alkali Metals
Visible light
No photoelectrons
Photoelectrons Photoelectrons
Visible light
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Experimental Set-up to study Photoelectric Effect:
Glass transmits only visible and infra-red lights but not UV light.
Quartz transmits UV light.
When light of suitable frequency falls on the metallic cathode, photoelectrons are
emitted. These photoelectrons are attracted towards the +ve anode and hence
photoelectric current is constituted.
UV light
K
● ●
V
+
μA
+
C A
W
C – Metallic cathode
A – Metallic Anode
W – Quartz Window
- Photoelectron
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1) Effect of Intensity of Incident Light on Photoelectric Current:
For a fixed frequency, the photoelectric current
increases linearly with increase in intensity of
incident light.
2) Effect of Potential on Photoelectric Current:
For a fixed frequency and intensity of
incident light, the photoelectric
current increases with increase in
+ve potential applied to the anode.
When all the photoelectrons reach
the plate A, current becomes
maximum and is known as saturation
current.
I
μA
Intensity (L)
0
0
Saturation Current
L1
L2
L2 > L1
This shows that even in the absence of accelerating potential, a few
photoelectrons manage to reach the plate on their own due to their K.E.
When –ve potential is applied to the plate A w.r.t. C, photoelectric current
becomes zero at a particular value of –ve potential called stopping potential
or cut-off potential.
When the potential is decreased,
the current decreases but does not
become zero at zero potential.
Intensity of incident light does not affect the stopping potential.
I
μA
+
Potential of A (V)
VS
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3) Effect of Frequency of Incident Light on Photoelectric Current:
For a fixed intensity of incident light, the photoelectric current does not depend on the
frequency of the incident light. Because, the photoelectric current simply depends on
the number of photoelectrons emitted and in turn on the number of photons incident
and not on the energy of photons.
4) Effect of Frequency of Incident Light on Stopping Potential:
I
μA
Potential of A (V)
0
VS1
+
Saturation Current
ν1
ν2
ν2 > ν1
VS2
For a fixed intensity of incident light, the
photoelectric current increases and is
saturated with increase in +ve potential
applied to the anode.
However, the saturation current is same
for different frequencies of the incident
lights.
When potential is decreased and taken
below zero, photoelectric current
decreases to zero but at different
stopping potentials for different
frequencies.
Higher the frequency, higher the stopping potential. i.e. VS α ν
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5) Threshold Frequency:
VS
(V)
0 ν0 ν
The graph between stopping potential and frequency does
not pass through the origin. It shows that there is a
minimum value of frequency called threshold frequency
below which photoelectric emission is not possible
however high the intensity of incident light may be. It
depends on the nature of the metal emitting photoelectrons.
i) For a given substance, there is a minimum value of frequency of incident light called
threshold frequency below which no photoelectric emission is possible, howsoever,
the intensity of incident light may be.
ii) The number of photoelectrons emitted per second (i.e. photoelectric current) is
directly proportional to the intensity of incident light provided the frequency is above
the threshold frequency.
iii) The maximum kinetic energy of the photoelectrons is directly proportional to the
frequency provided the frequency is above the threshold frequency.
iv) The maximum kinetic energy of the photoelectrons is independent of the intensity of
the incident light.
v) The process of photoelectric emission is instantaneous. i.e. as soon as the photon of
suitable frequency falls on the substance, it emits photoelectrons.
vi) The photoelectric emission is one-to-one. i.e. for every photon of suitable frequency
one electron is emitted.
Laws of Photoelectric Emission:
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Einstein’s Photoelectric Equation:
When a photon of energy hν falls on a metal surface, the energy of the photon is
absorbed by the electron and is used in two ways:
i) A part of energy is used to overcome the surface barrier and come out of the metal
surface. This part of the energy is called ‘work function’ (Ф = hν0).
ii) The remaining part of the energy is used in giving a velocity ‘v’ to the emitted
photoelectron. This is equal to the maximum kinetic energy of the photoelectrons (
½ mv2
max ) where ‘m’ is mass of the photoelectron.
Photon
hν
Metal
Photoelectron
According to law of conservation of energy,
hν = Ф + ½ mv2
max
= hν0 + ½ mv2
max
½ mv2
max = h ( ν - ν0 )
½ mv2
max
Ф = hν0
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Verification of Laws of Photoelectric Emission based on Einstein’s Photoelectric
Equation:
i) If ν < ν0, then ½ mv2
max is negative, which is not possible. Therefore, for
photoelectric emission to take place ν > ν0.
ii) Since one photon emits one electron, so the number photoelectrons emitted per
second is directly proportional to the intensity of incident light.
iii) It is clear that ½ mv2
max α ν as h and ν0 are constant. This shows that K.E. of the
photoelectrons is directly proportional to the frequency of the incident light.
iv) Photoelectric emission is due to collision between a photon and an electron. As
such there can not be any significant time lag between the incidence of photon and
emission of photoelectron. i.e. the process is instantaneous. It is found that delay is
only 10-8 seconds.
½ mv2
max = h ( ν - ν0 )
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Application of Photoelectric Effect:
1. Automatic fire alarm
2. Automatic burglar alarm
3. Scanners in Television transmission
4. Reproduction of sound in cinema film
5. In paper industry to measure the thickness of paper
6. To locate flaws or holes in the finished goods
7. In astronomy
8. To determine opacity of solids and liquids
9. Automatic switching of street lights
10. To control the temperature of furnace
11. Photometry
12. Beauty meter – To measure the fair complexion of skin
13. Light meters used in cinema industry to check the light
14. Photoelectric sorting
15. Photo counting
16. Meteorology
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Dual Nature of Radiation and Matter:
Wave theory of electromagnetic radiations explained the phenomenon of
interference, diffraction and polarization.
On the other hand, quantum theory of e.m. radiations successfully explained the
photoelectric effect, Compton effect, black body radiations, X- ray spectra, etc.
Thus, radiations have dual nature. i.e. wave and particle nature.
Louis de Broglie suggested that the particles like electrons, protons, neutrons, etc
have also dual nature. i.e. they also can have particle as well as wave nature.
Note: In no experiment, matter exists both as a particle and as a wave simultaneously.
It is either the one or the other aspect. i.e. The two aspects are complementary to
each other.
His suggestion was based on:
i) The nature loves symmetry.
ii) The universe is made of particles and radiations and both entities must be
symmetrical.
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de Broglie wave:
According to de Broglie, a moving material
particle can be associated with a wave. i.e. a
wave can guide the motion of the particle.
The waves associated with the moving material
particles are known as de
Broglie waves or matter waves.
Expression for de Broglie wave:
λ
According to quantum theory, the energy of the photon is E = hν =
hc
λ
According to Einstein’s theory, the energy of the photon is E = mc2
So, λ =
h
mc
or λ =
h
p
where p = mc
is momentum of a photon
If instead of a photon, we have a material particle of mass m moving with velocity
v, then the equation becomes
λ =
h
mv
which is the expression for de Broglie wavelength.
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Conclusion:
i) de Broglie wavelength is inversely proportional to the velocity of the particle. If
the particle moves faster, then the wavelength will be smaller and vice versa.
ii) If the particle is at rest, then the de Broglie wavelength is infinite. Such a wave
can not be visualized.
iii) de Broglie wavelength is inversely proportional to the mass of the particle. The
wavelength associated with a heavier particle is smaller than that with a lighter
particle.
iv) de Broglie wavelength is independent of the charge of the particle.
Matter waves, like electromagnetic waves, can travel in vacuum and hence they are
not mechanical waves.
Matter waves are not electromagnetic waves because they are not produced by
accelerated charges.
Matter waves are probability waves, amplitude of which gives the probability of
existence of the particle at the point.
λ =
h
mv
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Davisson and Germer Experiment:
●
●
F
V
θ
θ Ф
C
A
Nickel Crystal
A beam of electrons emitted by the
electron gun is made to fall on Nickel
crystal cut along cubical axis at a
particular angle.
The scattered beam of electrons is
received by the detector which can be
rotated at any angle.
The energy of the incident beam of
electrons can be varied by changing the
applied voltage to the electron gun.
Electron Gun
Intensity of scattered beam of electrons is
found to be maximum when angle of
scattering is 50° and the accelerating
potential is 54 V.
θ + 50° + θ = 180° i.e. θ = 65°
For Ni crystal, lattice spacing
d = 0.91 Å
Electron diffraction is similar
to X-ray diffraction.
For first principal maximum, n = 1
Bragg’s equation 2dsinθ = nλ gives
λ = 1.65 Å
Crystal Lattice
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Ф = 50°
Incident
Beam
Intensity of scattered beam at 54 V
Incident
Beam
Intensity of scattered beam at 44 V
Incident
Beam
Intensity of scattered beam at 48 V
Incident
Beam
Intensity of scattered beam at 64 V
According to de Broglie’s
hypothesis, h
λ =
2meV
de Broglie wavelength of
moving electron at V = 54
Volt is 1.67 Å which is in
close agreement with 1.65 Å.
12.27 Å
λ =
V
or
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√ V
0 5 10 15 20 25
(√ 54) V
Intensity
Diffraction
pattern after
100 electrons
Diffraction
pattern after
3000 electrons
Diffraction
pattern after
70000 electrons
Intensity vs √ Anode Potential:
End of Dual Nature of Matter and Radiations