2nd Sem M6 Physics Atomic Physics (Planks & Bohr's)

Atomic Physics

​Teacher Lady

Learning Objectives:​

By the end of this lesson, you will understand the significance of Max Planck's hypothesis and Niels Bohr's atomic theory, how they changed the understanding of atomic structure, and their impact on the development of quantum mechanics.

Planck’s Theory

Backgroud

​At the end of the 19th century, scientists were puzzled by the nature of radiation emitted by hot objects. Classical physics could not explain the observed spectra of light emitted by black bodies (objects that absorb and emit all frequencies of light).

​Planck's Solution:
Max Planck proposed that energy is not emitted or absorbed continuously but in discrete amounts called quanta. This was a revolutionary idea because it contradicted classical physics, which assumed that energy was continuous.

Planck’s hypothesis is often described as follows:

• Energy is quantized: energy can only exist in specific, discrete amounts, and the energy of each quantum is proportional to the frequency of the radiation.

• E = hf

Multiple Choice

Max Planck proposed that energy is not emitted or absorbed continuously but in discrete amounts called _______.

• Max Planck's Theory

• quanta

• Planck's Law

Multiple Choice

It is Planck’s hypothesis about energy can only exist in specific, discrete amounts, and the energy of each quantum is proportional to the frequency of the radiation.

• quanta

• Planck's Law

• Energy is quantized

• none of the above

Multiple Choice

As the frequency of an electromagnetic wave increases, the amount of energy in that wave ___________.

• increases.
• decreases.
• stays the same.

Multiple Choice

In Planck's energy equation, what is λ?

• speed of light

• Planck's constant

• energy

• wavelength

• frequency

Multiple Choice

In Planck's energy equation, what is h?

• speed of light

• Planck's constant

• energy

• wavelength

• frequency

Backgroud
​By the early 20th century, the study of atomic spectra (the colors of light emitted by atoms when heated or electrified) revealed patterns that classical physics could not explain. Specifically, the hydrogen atom emitted light at specific wavelengths, which suggested that the electron in the hydrogen atom existed in certain allowed orbits.

​Bohr’s Contribution:

Niels Bohr built upon Planck’s idea of quantization to explain the behavior of electrons in atoms. In his atomic model, Bohr proposed that:

1. Quantized Energy Levels:

   • Electrons in atoms occupy only certain allowed orbits with specific, quantized energies.

   • These orbits are stable, and electrons do not radiate energy while in these orbits.

2. Electron Transitions:

   • When an electron moves from one orbit to another, it emits or absorbs a photon of light. The energy of the photon corresponds to the difference in energy between the two orbits.

   • The energy of the photon emitted or absorbed is given by:

Summary: Connecting Planck’s Hypothesis and Bohr’s Atomic Theory

• Planck’s Hypothesis: Energy is quantized and can only exist in discrete amounts, forming the basis for understanding phenomena like radiation and atomic transitions.

• Bohr’s Atomic Theory: Uses Planck’s hypothesis to describe the behavior of electrons in atoms, explaining the discrete energy levels and electron transitions that give rise to atomic spectra.

Both theories were foundational in the development of quantum mechanics, which would later evolve into the modern quantum mechanical model of the atom.

Multiple Choice

Bohr is the first to give definite information regarding which subatomic particle?

• electron

• proton

• neutron

Multiple Choice

What do we call the area in which electrons are located?

• the electron sky

• the electron space

• the electron cloud

• the electron solar system

Multiple Choice

What do we call the area in which electrons are located?

• the electron sky

• the electron space

• the electron cloud

• the electron solar system

Multiple Choice

In Planck's energy equation, what is E?

• speed of light

• Planck's constant

• energy

• wavelength

• frequency

Multiple Choice

Niels Bohr built upon Planck’s idea of quantization to explain the behavior of electrons in atoms.

• false

• true

Multiple Choice

Planck’s Hypothesis states that energy is quantized and can only exist in discrete amounts, forming the basis for understanding phenomena like radiation and atomic transitions.

• true

• false

Multiple Choice

Bohr’s Atomic Theory uses Planck’s hypothesis to describe the behavior of protons in atoms, explaining the discrete energy levels and electron transitions that give rise to atomic spectra.

• False

• true

Photon

a tiny particle that comprises waves of electromagnetic radiation.

Move at the speed of light

Quantized

only specific values are allowed

Quantum Mechanics

study of the motion of objects that are atomic or subatomic in size and thus demonstrate wave-particle duality.

Electrons behave like waves and particles. We cannot specify accurately the location of an electron. All we can say is that there is a probability that it exists within this certain volume of space.

Atomic Emission Spectra

Ground state of an atom is the lowest energy state of the atom. When those atoms are given energy, the electrons absorb the energy and move to a higher energy level.

Atomic Emisions Spectra

Excited state of an atom is a state where its potential energy is higher than the ground state.

An atom in the excited state is not stable. When it returns back to the ground state, it releases the energy that it had previously gained in the form of electromagnetic radiation

Atomic Emission Spectrum

is the pattern of lines formed when light passes through a prism to separate it into the different frequencies of light it contains.

Multiple Choice

What is quantum theory? Select the best answer.

• The theory that all living things have mass.

• The theory that describes states of matter.

• The theory that was created to explain everything

• The theory that explains the behavior of matter and energy on atomic and subatomic levels.

Multiple Choice

Albert Einstein took Planck's theory, shot a beam of light onto a metal surface, which caused electrons to be emitted. This emission is called _________.

• speed of light

• Planck's constant

• Electron effect

• Photoelectric effect

• frequency

Multiple Choice

Albert Einstein found out the number of electrons that were ejected from the metal was proportional to the ______ of light.

• wavelength

• Planck's constant

• brightness

• Photoelectric effect

• frequency

Multiple Choice

Albert Einstein also notes that the energy of light must be above a certain frequency, or what we called __________, for an electron to be ejected.

• threshold frequency

• Planck's constant

• brightness

• Photoelectric effect

• frequency

Multiple Choice

In Planck's energy equation, what is c?

• speed of light

• Planck's constant

• energy

• wavelength

• frequency

Multiple Choice

What is the typical units of measurement for the "E" in the following equation: 
E_photon= h x f

• joules
• meters
• meters/seconds
• hertz

Multiple Choice

What is the energy of light whose wavelength is 4.06 x 10^-11 m? 

• 2.69 x 10^-44 J
• 1.63 x 10^-23 J
• 4.90 x 10^-15 J
• 8.97 x 10^{-53 J}

Multiple Choice

It is the study of the motion of objects that are atomic or subatomic in size and thus demonstrate wave-particle duality.

• Quantum physics

• Planck's Law

• Quantum mechanics

Multiple Choice

It is the state of an atom is the lowest energy state of the atom.

• Stable state

• Excited state

• Ground state

Multiple Choice

It is a state of an atom where its potential energy is higher than the ground state.

• Stable state

• Excited state

• Ground state

Multiple Choice

An atom in the excited state is not stable.

• True

• False

• Maybe

Black Body Radiation
https://www.youtube.com/watch?v=DHG61XPuWyk

Open Ended

Instruction: Copy the link to a browser

https://phet.colorado.edu/sims/html/blackbody-spectrum/latest/blackbody-spectrum_all.html

Identify the color of the black body with the given temperature

EXAMPLE :
6,050 K = BLUE

1. 800 K
2. 4950 K
3. 1300K
4. 3500 K
5. 5600 K

PHOTOELECTRIC
EFFECT

Multiple Select

How does light behave as a wave?

• Light reflects

• Light refracts

• Light diffracts

• Light reacts

Multiple Choice

Is light a wave or a particle?

• Light is light

• Light is particle only

• Light is a wave only

• Light is a mixture of wave and particle nature

Multiple Choice

In wave theory about light, the intensity of light depends on _______.

• wavelength

• frequency

• amplitude

• number of photons arrival

Multiple Choice

In wave theory about light, the smaller the amplitude, the ______ the intensity.

• higher

• lower

• the same

• none of the above

Multiple Choice

In wave theory about light, the _______ the amplitude, the higher the intensity.

• higher

• lower

• smaller

• larger

Multiple Choice

In wave theory about light, the larger the amplitude, the higher the intensity will have ______ light.

• higher

• dim

• bright

• larger

Multiple Choice

In wave theory about light, the smaller the amplitude, the lower the intensity will have ______ light.

• higher

• dim

• bright

• larger

Multiple Choice

In photon theory about light, the intensity of light depends on _______.

• wavelength

• frequency

• amplitude

• number of photons arrival

Multiple Choice

In photon theory about light, the fewer the photons, the ______ the intensity.

• higher

• lower

• the same

• none of the above

Multiple Choice

In photon theory about light, the _______ the photons, the higher the intensity.

• higher

• lower

• smaller

• larger

Multiple Choice

In photon theory about light, the larger the photons, the higher the intensity will have ______ light.

• higher

• dim

• bright

• larger

Multiple Choice

In photon theory about light, the fewer the photons, the lower the intensity will have ______ light.

• higher

• dim

• bright

• larger

Multiple Choice

In photon theory about light, what is the relationship between the energy and frequency?

• As frequency increases, energy decreases.

• As frequency increases, intensity also increases.

• As frequency increases, energy decreases.

• As frequency increases, energy also increases.

Multiple Choice

In wave theory about light, what is the relationship between the energy and intensity?

• As frequency increases, energy decreases.

• As energy increases, intensity also increases.

• As frequency increases, energy decreases.

• As frequency increases, energy also increases.

Multiple Choice

This is the phenomenon in which electrons are ejected from a material after absorbing a suitable frequency.

• Wave particle duality

• Photon Theory

• Wave Theory

• Photoelectric effect

Multiple Choice

What do you call the minimum energy required to eject an electron?

• Wave particle duality

• threshold frequency

• work function

• Photoelectric effect

Multiple Choice

In photon theory, kinetic energy of the emitted electrons depends on ________.

• amplitude

• frequency

• wavelength

• Photoelectric effect

Multiple Choice

In photon theory, the smaller the _______, the smaller the kinetic energy.

• amplitude

• frequency

• wavelength

• Photoelectric effect

Multiple Choice

In photon theory, the higher the frequency, the ______ the kinetic energy.

• smaller

• lower

• higher

• none of the above

​WAVE
PARTICLE DUALITY

Multiple Choice

All electromagnetic waves behaves like ______ and _____.

• wave , particle

• wave , light

• light , particle

• none of the above

Multiple Choice

What is the formula for solving the wavelength of light?

• λ= hp

• f=c/λ

• c=λf

• p = h/λ

Multiple Choice

What is the formula for solving the momentum of light?

• λ= hp

• f=c/λ

• c=λf

• p = h/λ