Planck's Quantum Theory | Chemistry

Summary

This script introduces Planck's quantum theory, explaining the concepts of continuous and discontinuous energy flow through the excitation and de-excitation of electrons. It clarifies the misconception of classical physics and highlights Planck's postulates, including the quantization of energy in the form of photons. The theory's applications in explaining monochromatic and polychromatic light are discussed, emphasizing the role of frequency and wavelength in determining photon energy and color.

Takeaways

• 🔬 Planck's quantum theory revolutionized the understanding of energy flow at the microscopic level.
• ⚛️ Electrons can jump between energy levels by absorbing or emitting fixed amounts of energy called quanta.
• 📉 Classical scientists believed in the continuous flow of energy, which Planck's theory disproved.
• 💡 Energy flow is continuous in macroscopic phenomena but discontinuous at the microscopic level.
• 🎢 In Bohr's atomic model, electrons lose fixed amounts of energy when moving between discrete energy levels.
• 🍫 Energy is quantized into discrete packets, similar to chocolate bars, and cannot be arbitrarily controlled.
• ✨ Planck's postulates state that energy is absorbed or emitted in discrete wave packets called quanta or photons.
• 🌈 Photons are the basic units of light, and their energy is proportional to their frequency.
• 🌀 Different colors of light have photons with different frequencies and wavelengths.
• 🔎 Monochromatic light consists of photons with the same energy, while polychromatic light, like sunlight, contains photons of various energies.

Q & A

What is the concept of excitation and de-excitation of an electron in the context of Bohr's atomic model?

In Bohr's atomic model, excitation refers to an electron absorbing energy to jump from a lower energy level to a higher one. De-excitation is the process where an electron releases energy and moves from a higher energy level back to a lower one, emitting the energy in the form of a photon.

What was the classical belief about the electron's energy absorption and loss before Planck's quantum theory?

Before Planck's quantum theory, it was believed that electrons absorbed or lost energy in a continuous manner, which was later proven incorrect by Planck's theory.

What is the main principle of Max Planck's quantum theory?

The main principle of Max Planck's quantum theory is that energy is absorbed or lost discontinuously, in the form of discrete packets or quanta, rather than continuously.

What is the difference between continuous and discontinuous flow of energy?

Continuous flow of energy is a concept where energy can be varied in a continuous range, like changing the potential energy of a ball by altering its height. Discontinuous flow of energy, on the other hand, occurs in fixed amounts or quanta, as seen in the energy transitions of electrons between atomic energy levels.

How does the concept of a discrete wave packet relate to Planck's quantum theory?

In Planck's quantum theory, a discrete wave packet represents a fixed amount of energy that is emitted or absorbed during a quantum transition. These packets are indivisible and unique, differing from one another in energy, frequency, and wavelength.

What are the postulates of Planck's quantum theory?

Planck's quantum theory postulates that energy is absorbed or emitted in a discontinuous manner, in discrete packets called quanta or photons, and that the energy of these quanta is directly proportional to their frequency, with Planck's constant (h) as the proportionality constant.

What is the significance of Planck's constant in the context of quantum theory?

Planck's constant (h) is a fundamental constant that quantifies the proportionality between the energy of a photon and its frequency. It is used in the equation E = hν, where E is the energy, h is Planck's constant, and ν is the frequency of the photon.

What is a photon and how is it related to the concept of quanta?

A photon is an elementary particle of light, representing the basic unit of electromagnetic radiation. It is a quantum of energy for light, having no rest mass, no charge, and traveling at the speed of light. Photons are emitted or absorbed in discrete packets of energy.

How does the energy of a photon depend on its frequency or wavelength?

The energy of a photon is directly proportional to its frequency (E = hν) and inversely proportional to its wavelength (E = hc/λ), where h is Planck's constant, c is the speed of light, and λ is the wavelength of the photon.

What is the application of Planck's quantum theory in explaining monochromatic and polychromatic light?

Planck's quantum theory helps explain that monochromatic light, such as red laser light, consists of photons of the same frequency, wavelength, and energy, while polychromatic light, like sunlight, is a mixture of photons of different frequencies, wavelengths, and energies, resulting in various colors.

How do the concepts of frequency and wavelength differentiate the colors in polychromatic light?

In polychromatic light, different colors are produced by photons with varying frequencies and wavelengths. For example, violet light has a higher frequency and shorter wavelength compared to red light, resulting in different photon energies and perceived colors.

Outlines

00:00

🔬 Quantum Theory and Energy Transitions

This paragraph introduces the fundamental concepts of Planck's quantum theory, focusing on the discontinuous nature of energy absorption and emission by electrons. It explains the process of excitation and de-excitation using an electron's transition between energy levels as an example. The classical view of continuous energy change is contrasted with Planck's revolutionary idea that energy changes occur in discrete amounts. The paragraph also introduces the concepts of continuous and discontinuous energy flow, using the analogy of a ball's potential and kinetic energy versus the quantized energy levels of an electron. The importance of understanding these concepts for grasping the essence of quantum theory is emphasized.

05:00

🌟 Understanding Discrete Energy Packets and Photons

The second paragraph delves deeper into the discontinuous flow of energy, describing it through the concept of discrete energy packets or quanta. It uses the analogy of chocolate packets to illustrate the individual and separate nature of these energy packets. The paragraph explains Planck's postulates, emphasizing that energy is absorbed or emitted in discrete amounts, not continuously. It introduces the term 'photon' to describe the elementary particles of light, which are quantized energy packets with no rest mass and travel at the speed of light. The relationship between the energy of a photon and its frequency is established through Planck's constant, highlighting the direct proportionality and the formula E = hν. The paragraph concludes with an explanation of how Planck's theory can be applied to understand monochromatic and polychromatic light, demonstrating the practical implications of quantum theory in everyday phenomena.

10:03

🌈 The Significance of Frequency and Wavelength in Quantum Theory

The final paragraph wraps up the discussion on Planck's quantum theory by highlighting the importance of frequency and wavelength in determining the characteristics of light and other electromagnetic radiation. It explains how different frequencies and wavelengths result in different colors and types of waves, underlining the diversity within the electromagnetic spectrum. The paragraph reinforces the understanding that photons, despite being elementary particles, exhibit variability due to their distinct frequencies and wavelengths. This summary serves as a conclusion, reinforcing the key points discussed in the previous paragraphs and encouraging further exploration of the applications and implications of quantum theory.

Keywords

💡Quantum Theory

Quantum theory is a fundamental framework in physics that describes the behavior of energy and matter at the smallest scales. It is the basis for understanding phenomena that classical physics cannot explain. In the video, quantum theory is central to explaining how energy is absorbed and emitted in discrete packets, or quanta, rather than continuously as was previously thought.

💡Excitation and De-Excitation

Excitation refers to the process by which an electron in an atom absorbs energy and moves to a higher energy level. Conversely, de-excitation is when the electron loses energy and returns to a lower energy level, often emitting a photon in the process. The script uses these concepts to illustrate the quantized nature of energy exchange at the atomic level, as opposed to the continuous energy exchange in macroscopic phenomena.

💡Bohr's Atomic Model

Bohr's atomic model is an early quantum theory of the atom where electrons orbit the nucleus in quantized energy levels. The model explains the stability of atoms and the quantized nature of atomic spectra. In the script, this model is used to describe the electron's movement between energy levels and the quantized energy changes that occur during excitation and de-excitation.

💡Continuous Flow of Energy

Continuous flow of energy refers to the classical idea that energy can change in an unbroken and uninterrupted manner. The script contrasts this with the discontinuous flow of energy at the quantum level, using the example of a ball falling to demonstrate how energy can be varied continuously in everyday life.

💡Discontinuous Flow of Energy

Discontinuous flow of energy is a concept introduced by Planck's quantum theory, where energy is absorbed or emitted in discrete amounts rather than in a smooth, continuous manner. The script explains this with the electron transitions between energy levels, which can only lose or gain specific amounts of energy, represented by quanta or photons.

💡Quanta

Quanta (plural) or quantum (singular) are the discrete packets of energy that are exchanged during quantum transitions. They are fundamental to the concept of energy quantization. The script uses the term to describe the fixed amounts of energy that an electron emits or absorbs when changing energy levels.

💡Photon

A photon is a quantum of light and all other forms of electromagnetic radiation. It is the basic unit of light, carrying energy and having zero mass. The script explains that light is made up of photons, each with a specific energy determined by its frequency, and that the energy of photons is quantized.

💡Planck's Constant

Planck's constant (denoted as 'h') is a fundamental physical constant that relates the energy of a photon to its frequency. With a value of approximately 6.626 x 10^-34 joule seconds, it is used in the equation E = hν to calculate the energy of a photon. The script mentions this constant as a key element in understanding the quantization of energy.

💡Frequency

Frequency, in the context of the script, refers to the number of cycles of a wave that occur per unit of time and is directly proportional to the energy of a photon. Higher frequency light, such as blue light, has more energy than lower frequency light, such as red light. The script uses frequency to explain the different energies of photons and the resulting colors of light.

💡Wavelength

Wavelength is the distance between two consecutive points in a wave that are in the same phase. It is inversely related to frequency, meaning that a longer wavelength corresponds to a lower frequency and vice versa. The script explains how the wavelength of light determines its color and energy, with shorter wavelengths (like violet) having higher energies than longer wavelengths (like red).

💡Monochromatic and Polychromatic Light

Monochromatic light consists of a single color and is made up of photons of the same wavelength and frequency. Polychromatic light, on the other hand, is composed of multiple colors, each with different wavelengths and frequencies. The script uses these terms to illustrate how Planck's quantum theory can explain the composition of light, whether it is a single color or a mixture of many colors like sunlight.

Highlights

Introduction to the concept of excitation and de-excitation of an electron in an atom according to Bohr's atomic model.

Explanation of how an electron absorbs 10.2 electron volts to jump from one energy level to another.

Clarification of the misconception in classical physics regarding continuous energy absorption or loss by electrons.

Max Planck's introduction of quantum theory in 1900, proposing energy absorption and loss occur discontinuously.

The concept of continuous energy flow in everyday life, exemplified by a ball's potential and kinetic energy.

Introduction of discontinuous energy flow at the microscopic level, contrasting with the macroscopic world.

Description of electron transitions between energy levels in Bohr's model and the quantized energy loss during these transitions.

The impossibility of controlling the quantized energy loss during electron transitions, as opposed to continuous energy flow.

Max Planck's assertion that energy at the microscopic level flows in discrete packets, not continuously.

Explanation of the term 'quanta' or 'photons' as discrete packets of energy in the context of light.

The elementary particle of light, the photon, is described as having no charge or rest mass and travels at the speed of light.

Planck's quantum theory postulates that energy is absorbed or emitted in a discontinuous manner.

The relationship between the energy of a photon and its frequency, introduced by Planck's constant (h = 6.626 x 10^-34 joule second).

The energy of a photon is directly proportional to its frequency and inversely proportional to its wavelength.

Application of Planck's quantum theory to explain monochromatic and polychromatic light, including the composition of sunlight.

The significance of frequency and wavelength in determining the color and nature of different types of light.

Final note on the uniqueness of photons due to their distinct frequencies and wavelengths, contributing to the diversity of light.

Transcripts

plunk's quantum theory concept of

continuous and discontinuous flow of

energy and applications of planck's

quantum theory

firstly let me teach you the concept of

excitation and de-excitation of electron

let's consider an atom

that this electron is present in first

energy level according to bohr's atomic

model energy is needed by this electron

to jump from first energy level to

second energy level

let i provide 10.2 electron volt energy

to this electron it will be excited and

will move from first energy level to

second energy level after some time this

electron will be de-excited it will give

off or radiate the same amount of energy

10.2 electron volt to the surrounding

now listen carefully in old times a

classical period scientists believe that

an electron absorbs or loses energy

continuously which is totally wrong

in 1900 max planck put forward his

famous quantum theory

according to this theory electron

absorbs or loses energy discontinuously

which is hundred percent right this

theory revolutionarized the signs and

opened new doors for different

discoveries

now i am going to teach you the concept

of continuous flow and discontinuous

flow of energy believe me if you

understand this concept you understand

the planck's quantum theory which no one

is teaching us in the school or college

course remember that continuous flow of

energy happens in our daily life while

discontinuous flow of energy happens at

microscopic level

firstly let me teach you the concept of

continuous flow of energy consider a

ball present at certain height above the

ground we know that it possesses

potential energy now when this ball

falls toward the ground its potential

energy is converted to kinetic energy

here comes the most important question

can i change the value of potential

energy or kinetic energy of this ball

well the answer is yes it is in my

control i can change its value the next

question is how can i change its value

well it is simple change the height of

the ball to desired level and the values

of potential energy and kinetic energy

would be changed it means that it is in

my control to change the values of

potential energy and kinetic energy to 5

joule

6 joule 7 joule 8 joule etc

therefore we say that in this case

energy flow and continuous way our flow

of energy is continuous because i can

control it or i can change

now coming to the concept of

discontinuous flow of energy

according to bohr's atomic model

electron can reside in different energy

levels like first energy level second

energy level third energy level and

fourth energy level like steps of a

ladder now consider electron at highest

energy level fourth energy level

let this electron jumps from fourth

energy level to third energy level when

it jumps from higher energy level to

lower energy level it loses a radiate

energy let it loses 15 joule energy

secondly this electron jumps from third

energy level to second energy level and

also loses 11 joule energy

thirdly it jumps from second energy

level to first energy level and it loses

4 joule energy now listen carefully i am

interested that when an electron jumps

from 4th energy level to 3rd energy

level it should lose only 14 joule

energy when it jumps from third energy

level to second energy level it should

lose only 13 joule energy and when it

jumps from second energy level to first

energy level it should lose only 12

joule energy i mean the flow of energy

must be continuous 14 joule 13 joule 12

joule according to my wishes

now let me ask you is it possible

well here comes mix planck baba that it

is not possible and it is totally wrong

energy flow and discontinuous manner at

microscopic level plunk baba says that

when electron jumps from fourth energy

level to third energy level it lose

fixed amount of energy 15 joule energy

in the form of discrete wave packet

like this

are just like a chocolate packet

noted down that the word discrete means

individually separate or unique

we will learn more about wave packet

later in this lecture

secondly when an electron jumps from

third energy level to second energy

level it will lose another discrete wave

packet of energy like this chocolate

pack thirdly when an electron jumps from

second energy level to first energy

level it will again lose another

discrete 12 packet of energy like this

chocolate bag this web packet of energy

is totally different from this wave

packet of energy while this web packet

of energy is also totally different from

this wave packet of energy so max planck

baba states that the energy of each wave

packet is fixed or quantized for example

this way packet has quantized energy of

15 joule this wave packet of energy has

quantized energy of 11 joule and this

wave packet of energy has quantized

energy of 4 joule therefore energy

discontinuously flow or the flow of

energy is discontinuous because it is

already fixed and we cannot control them

hence noted down the concept of

continuous flow and discontinuous flow

of energy

now let's understand the postulates of

planck's quantum theory he states that

energy absorbed or emitted by a body is

in a discontinuous manner not in a

continuous manner

secondly he states that a body absorb a

image energy and discrete wave packets

these web packets are called quanta or

in case of light it is called photon

remember that quanta is plural and

quantum is singular so note it down that

whenever i say quanta quantum or photon

in this lecture it will always mean wave

packets

now what is quanta are photon

well

photon or quanta is the elementary

particle of light or we can say it is

the basic unit of light it means that

every light or radiation is made up of

billions or trillions of photons

photons are nothing but they are made up

of electric field and magnetic field

they have no charge they have no rest

mass and they travel at the speed of

light

thirdly the energy of protons are quanta

is directly proportional to the

frequency

e is directly proportional to mu

for example

consider blue photon and red photon the

frequency of blue photon is high and the

frequency of red photon is low so the

energy of blue photon is high and that

of rate photon is low

now to eliminate the sign of

proportionality we put h which is known

as a planck's constant and its value is

6.626

into 10 to the power negative 34 joule

second also we know that frequency is

equal to c upon lambda so put the value

of frequency in this equation we get e

is equal to h into c upon lambda so

remember that energy of photon depends

upon frequency wavelength of wave number

just noted down these postulates of

planck's quantum theory

finally let me teach you the application

of planck's quantum theory we can easily

understand and explain the monochromatic

light and polychromatic light by the

help of planck's quantum theory

we know that monochromatic light means

light of one color like red laser light

while polychromatic light means light of

many colors

like sunlight this monochromatic red

light is made up of one type of photon

red photon

all the photons have same wavelength

same frequency and same energy

therefore we see them red light

while the sunlight is a mixture of seven

lights like violet indigo blue green

yellow orange and red

the photon of foil it is different from

indigo because they both have different

wavelength frequency and energy

similarly these all colors have

different photons but overall they make

up a white light which we can see as a

sunlight

here let me give you one last bonus tape

photons are different from one another

due to difference in frequency and

wavelength so only these two parameters

make different colors different waves

etc

i hope that you have understood the

concept of planck's quantum theory