Planck's Quantum Theory: Continuous and Discontinuous Flow of Energy
Excitation and De-excitation of Electrons
Excitation: Electron absorbs energy to move to a higher energy level.
Example: Absorbing 10.2 eV to move from the first to the second energy level.
De-excitation: Electron releases the absorbed energy to return to a lower energy level.
Example: Releasing 10.2 eV to surroundings.
Classical View: Continuous absorption and release of energy (incorrect).
Quantum Theory: Discontinuous absorption and release of energy (correct, proposed by Max Planck in 1900).
Continuous Flow of Energy
Definition: Energy change that can be controlled and modified.
Example: A ball at height having potential energy that converts to kinetic energy when it falls.
Changing the height alters potential and kinetic energy values (can be 5 J, 6 J, 7 J, etc.).
Key Point: Continuous flow as energy values can be varied and controlled.
Discontinuous Flow of Energy
Definition: Energy change occurs in fixed packets (quanta) and cannot be controlled.
Bohr's Atomic Model: Electrons reside in fixed energy levels.
Example: An electron loses 15 J moving from the 4th to 3rd energy level, 11 J from 3rd to 2nd, and 4 J from 2nd to 1st.
Max Planck’s Contribution: Energy transitions happen in discrete packets called quanta (or photons for light).
Each packet of energy is fixed and unique (discrete).
Examples: 15 J, 11 J, and 4 J energy packets.
Postulates of Planck’s Quantum Theory
Energy Absorption/Emission: Always discontinuous, not continuous.
Energy Carriers: Wave packets called quanta (or photons in case of light).
Quanta: Plural form.
Quantum: Singular form.
Photon: Basic unit of light.
Nature of Photons: Made of electric and magnetic fields, no charge, no rest mass, travel at the speed of light.
Energy Proportional to Frequency:
Equation: E ∝ μ (frequency).
Example: Blue photon (high frequency, high energy) vs. Red photon (low frequency, low energy).
Planck's constant (h): 6.626 x 10^-34 J s.
Frequency formula: E = h * c / λ (wavelength).
Applications of Planck’s Quantum Theory
Monochromatic Light: Light of one color (e.g., red laser light) made of identical photons (same wavelength, frequency, and energy).
Polychromatic Light: Light of many colors (e.g., sunlight) which is a mixture of different photons (violet, indigo, blue, green, yellow, orange, red), each with unique wavelength, frequency, and energy.
Bonus Tip: Photons differ due to variations in frequency and wavelength, creating different colors and waves.
Conclusion
Key Takeaway: Planck’s Quantum Theory introduces the concept of energy quantization, revolutionizing our understanding of how energy is absorbed and emitted at microscopic levels.