Electromagnetic Spectrum

Electromagnetic spectrum ranges from Radiowaves to Gamma waves. - Form of energy - Shorter wavelength -> Higher frequency -> Higher energy - Longer wavelength -> Lower frequency -> Lower energy

Electromagnetic radiation •Travel at speed of light, c = fλ -> 3.0 x 108 m/s •Light Particle – photon have energy given by -> E = hf •Energy photon - proportional to frequency, f

Inverse relationship between- λ and f Wavelength, λ - long

Frequency, f - low

Wavelength, λ - short Frequency, f - high

Plank constant • proportionality constant bet energy and freq

Excellent video wave propagation

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Electromagnetic Wave propagation.

Wave

Electromagnetic radiation

Electromagnetic radiation • Moving charges/particles through space • Oscillating wave like property of electric and magnetic field • Electric and magnetic field oscillate perpendicular to each other and perpendicular to direction of wave propagation.

Electromagnetic wave propagation

Wave – wavelength and frequency - travel at speed of light

Violet

λ = 410nm

Red

f = c/λ = 3 x 108/410 x 10-9

= 7.31 x 1014 Hz

E = hf = 6.626 x 10-34 x 7.31 x 1014

= 4.84 x 10-19 J

λ = 700nm

f = c/λ = 3 x 108/700 x 10-9

= 4.28 x 1014 Hz

E = hf = 6.626 x 10-34 x 4.28 x 1014

= 2.83 x 10-19 J

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Electromagnetic Wave propagation.

Wave

Electromagnetic radiation

Simulation on Electromagnetic Propagation

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Electromagnetic radiation • Moving charges/particles through space • Oscillating wave like property of electric and magnetic field • Electric and magnetic field oscillate perpendicular to each other and perpendicular to direction of wave propagation.

Wave – wavelength and frequency - travel at speed of light

Electromagnetic wave propagation

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Electromagnetic Wave

Violet

λ = 410nm

Red

f = c/λ = 3 x 108/410 x 10-9

= 7.31 x 1014 Hz

λ = 700nm

f = c/λ = 3 x 108/700 x 10-9

= 4.28 x 1014 Hz

Which light wave have higher frequency, if both have same speed reaching Y same time?

Violet light

Y

Red light

X

Wavelength – Distance bet two point with same phase, bet crest/troughs – unit nm Frequency – Number of cycle/repeat per unit time (cycles in 1 second) – unit Hz

Click here on excellent video red /violet wave

Light travel same speed Red flippers – long λ - less frequent Violet shoes – short λ - more frequent

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Particles /photon •single slit – single band •double slit – double band

Wave •Crest/trough appearing •Double slit – interference behind screen – bright/dark bands

Principle of wave–particle duality.

Quantum particles – small particles, like electrons – Is light/electron a Wave or Particle?

Single electron behave like particles but travel like a wave

Quantum Weirdness – Is Light/electron a Wave or Particle?

Pass BIG particles through a 2 slit Pass waves through a 2 slit

Particle gun Slit

2 bands Interference patterns of many bands

Pass electron through a 2 slit

Conclusion

Interference patterns of many bands

Does electron behave as

Particles

Waves

Waves

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Particles/photon •single slit – single band •double slit – double band

Waves •Crest/trough appearing •Double slit – interference behind screen – bright/dark bands

Principle of wave–particle duality. Wave of possibility.

Single electron behave like particle but travel like a wave

Pass electron through a 2 slit

Interference patterns of many bands

Particles

Waves

Pass electron through a 2 slit

Measuring /observing it - which slit it passes through

Waves

Particles

Particles/photon •single slit – single band •double slit – double band

Waves •Crest/trough appearing •Double slit – interference behind screen – bright/dark bands

Quantum Weirdness – Is Light/electron a Wave or Particle?

Does electron behave as

Does electron behave as

Conclusion

Try to measure it.

Is light a Wave or Particle?

Is Light a Wave or Particle?

VS

Current measured

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Wave Theory Particle Theory

Particle Theory •Light energy comes in tiny packets -photons •Amt energy directly proportional to frequency, E = hf •Red light – low freq – low energy •Blue light – high freq – high energy

Wave Theory •Light energy arrives continuously, regardless of freq •Energy proportional to amplitude •Intensity light – depends on amplitude •Low intensity – low amplitude •High intensity – high amplitude

Photoelectric effect

Electrons are release (photoelectrons)

Light hits metal

Light – Shows photoelectric effect Shine light to metal Current measured

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Is Light a Wave or Particle?

Is light a Wave or Particle?

Is Light a Particle or Wave?

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Wave Theory Particle Theory

Wave Theory •Light energy arrives continuously, regardless of freq •Energy proportional to amplitude •Intensity light – depends on amplitude •Low intensity – low amplitude •High intensity – high amplitude

Light – Shows photoelectric effect Shine light to metal Current measured

Is Light a Wave or Particle?

Wave Theory

Low intensity – Low amplitude High intensity –High amplitude

Particle Theory

Red light Low frequency – Low energy

Blue light High frequency – High energy

Colour/Frequency light Intensity light Colour/Frequency light Colour/Frequency light

Light energy arrives continuously, regardless of frequency

Particle Theory •Light energy comes in tiny packets -photons •Amt energy directly proportional to frequency, E = hf •Red light – low freq – low energy •Blue light – high freq – high energy

Is light a Wave or Particle?

VS

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Is Light a Wave or Particle?

Wave Theory

No electrons released

Particle Theory

Colour/Frequency light Intensity light Colour/Frequency light Colour/Frequency light

If light is Wave • Colour/Intensity of light NOT important ! • Regardless of colour/freq/intensity

Shine light LONG enough

If light is Particle • Colour/Frequency of light is important !

Shine RED light Shine BLUE light

Electrons are released No electrons released Result!

Red light Low freq – Low energy

Blue light High freq – High energy

Are electrons released?

Is light a Wave or Particle?

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Stream of light

Is Light a Wave or Particle?

Stream of photon Fixed amt of energy – E = hf

Is Light a Wave or Particle?

Is Light a Wave or Particle?

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Video Is Light a Wave or Particle?