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Understanding Classical and Modern Physics: Matter, Light, and Quantum Theory

This overview delves into the foundational concepts of classical and modern physics, focusing on the nature of matter and light. Classical physics examines larger objects and behaves according to Newtonian principles, while modern physics, influenced by Einstein, addresses particle-wave duality, especially at the atomic and quantum levels. The photoelectric effect illustrates how light behaves as both a particle and wave, revealing its dual properties. This discussion also introduces key principles such as quantum energy, frequency, and the relationship between energy and wavelength, essential for grasping contemporary physics.

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Understanding Classical and Modern Physics: Matter, Light, and Quantum Theory

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  1. _______________physics • Matter is a____________________ • Light is a _________________. Classical particle wave This is "everyday" physics that deals with objects that are relatively 1. _____________  bigger than _____________ 2. _____________  v << _____ large atoms slow c Einstein _______________ modified classical physics so that it would give more accurate results when speeds _______________________________ and for________________. His theories are called the ________________ and ________________ Theories of _________________________ . were close to c gravity Special General Relativity

  2. Modern • _______________ physics modified physics to deal with • _________________________ on the scale of ___________ . • According to this theory: • Matter can act like a___________________________. • Light can act like a___________________________. atoms tiny objects particle or a wave particle or a wave Ex: Light in the classical view acts like a ___________ whose _________________ determines its energy: wave amplitude brighter • _______________  more____________ energy

  3. Ex: The ___________________ effect showed that light can act like a ______________________ . photoelectric particle shine light electrons e- “photo…” “…electric” zinc

  4. Duality: wave particle

  5. Einstein _____________________________ for a paper that explained the photoelectric effect by assuming light acted like ______________. The higher its _______________ the greater the energy of the light particle. Bright light consists of ___________ particles. won a Nobel Prize frequency particle many dim red low _______________ light:  1_______ energy particle cannot eject an e- none of these many _______ energy particles could eject an e- low bright red ________________light: dim violet high ________________light:  1_______ energy particle can eject 1 e- each of these many ________ energy particles could eject an e- high bright violet ________________light:

  6. The ______________ (basic unit) of electromagnetic energy (light) is called a _______________ . It has no mass, but carries ______________ and ________________ . Its energy is given by: quantum photon energy momentum Eph = where h = = Ex: What is the relationship between Eph and f? Eph f What quantity does the slope of the line?

  7. See page 1 of Reference Tables

  8. Page 1: top

  9. The ______________ (basic unit) of electromagnetic energy (light) is called a _______________ . It has no mass, but carries ______________ and ________________ . Its energy is given by: quantum photon energy momentum Eph = hf where h = = Planck's constant 6.63 x 10-34 J·s Ex: What is the relationship between Eph and f? Eph f h What quantity does the slope of the line? Eph/f = ?

  10. Ex: What is the relationship between Eph and l? • Start with the equation: • Substitute c in for v: • Solve for f: • Substitute in the equation for v = fl c = fl f = c/ l Eph= hf Eph= hc/l Ex: What is the relationship between Eph and l in graph form? Eph l The greater the wavelength, the ___________ the energy.

  11. Ex: What is the relationship between Eph and l? • Start with the equation: • Substitute c in for v: • Solve for f: • Substitute in the equation for v = fl c = fl f = c/ l Eph= hf Eph= hc/l Ex: What is the relationship between Eph and l in graph form? Eph l less The greater the wavelength, the ___________ the energy.

  12. Ex: Find the energy of a blue light photon in joules. Eph = hf = hc/l = (6.63 x 10-34 J·s) (???) Convert the answer to electronvolts (eV). page 1 of RT: 1 eV = ________________ J

  13. Choose f = 6.5 x 1014 Hz

  14. Ex: Find the energy of a blue light photon in joules. Eph = hf = hc/l = (6.63 x 10-34 J·s) (6.5 x 1014 Hz) = 4.3 x 10-19 J Convert the answer to electronvolts (eV). page 1 of RT: 1 eV = ________________ J

  15. Page 1: top

  16. Ex: Find the energy of a blue light photon in joules. Eph = hf = hc/l = (6.63 x 10-34 J·s) (6.5 x 1014 Hz) = 4.3 x 10-19 J Convert the answer to electronvolts (eV). 1.6 x 10-19 See page 1 of RT: 1 eV = ________________ J _______1 eV_______ 1.6 x 10-19 J Eph = 4.3 x 10-19 J x Eph = 2.7 eV

  17. _____________ theory - ____________________ energy is emitted from and absorbed by _______________ in _____________ amounts or ________________ . ( ______________ means "separate, individual pieces.") Quantum electromagnetic matter discrete "packets" Discrete after: absorption before: Ex: _______________ of a photon atom has ______ energy atom more emission Ex: _____________ of a photon after: before: atom has _______ energy atom less

  18. Compton Ex The ____________Effect: X-rays scatter off electrons. 0 e- at rest  KE =____ v=c before collision: x-ray _______ photon now has KE e- ____________ after collision: The scattered photon now has _______ energy. So its f is _______ and its l is ______________ less less c longer momentum energy Both _________________and ______________ are conserved.

  19. In sum, light can act like a __________________ or like a ____________ . Which one it acts like depends on the situation. When light interacts with.. particle wave … __________ , it acts like a _________________ Examples: 1/ __________________ 2/ __________________ … ___________ , it acts like a __________________ Examples: 1/ __________________ 2/ __________________ 3/ __________________ light atoms wave particle interference absorption diffraction emission collisions Even when it is described as a photon, we still use __________ properties such as _______________ and _________________ to describe it. frequency wave wavelength

  20. Electron charge: In 1909, Millikan sprayed drops of ________ into an _______________ field E. oil electric qE Fe =___ oil drop mg Fg =_____ By suspending the oil drop then letting it fall, he was able to discover that the oil drops always carried an ___________________________ of the fundamental charge = ______________________ (the ______________ of charge). which is the charge on 1 _____________ or _____________ .  Charge is __________________ . integer multiple 1.6 x 10-19 C quantum electron proton quantized

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