Photoelectric Effects Facts And Prospects L-2 Photoelectric Effects Facts and Prospects
→ \rightarrow → → \rightarrow → Photoelectric Effects Facts and Prospects → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Photo electric Effect Time Line
→ \rightarrow → → \rightarrow → Photo electric Effect Time Line → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 1905- Annus Mirabilis(The Miraculous Year)
Photoelectric effect
Special Relativity
Brownian motion Molecular hypothesis
Photoelectric Effects Facts and Prospects → \rightarrow → → \rightarrow → 1905- Annus Mirabilis(The Miraculous Year) → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Universality Millikan
Photo electric Effect Time Line → \rightarrow → → \rightarrow → Universality Millikan → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Important Points
Intensity - Frequency Interplay
Minimum frequency required for photoemission
Proportional to Intensity beyond the minimum frequency
No emission below the minimum frequency
Linear Relation between the frequency and the stopping potential
Universality: Millikan
Ack: Millikan + Wiki
1905- Annus Mirabilis(The Miraculous Year) → \rightarrow → → \rightarrow → Important Points → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 The Mystery of Photoelectric Effect
Universality Millikan → \rightarrow → → \rightarrow → The Mystery of Photoelectric Effect → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Monochromatic Plane Wave
E ⃗ = E 0 → sin ( k Ƶ − ω t ) \vec{E}=\overrightarrow{E_0} \sin (k Ƶ -\omega t) E = E 0 sin ( k Ƶ − ω t )
U = ϵ 0 E ⃗ 0 2 U=\epsilon_0 \vec{E}_0^2 U = ϵ 0 E 0 2
= ϵ 0 E ⃗ 0 2 sin 2 ( k Ƶ − ω t ) = \epsilon_0 \vec{E}_0^2 \sin ^2(k Ƶ-\omega t) = ϵ 0 E 0 2 sin 2 ( k Ƶ − ω t )
⟨ U ⟩ = ϵ 0 E ⃗ 0 2 2 \langle U\rangle=\frac{\epsilon_0 \vec{E}_0^2}{2} ⟨ U ⟩ = 2 ϵ 0 E 0 2
Important Points → \rightarrow → → \rightarrow → Monochromatic Plane Wave → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 The Mystery of Photoelectric Effect
The Mystery of Photoelectric Effect → \rightarrow → → \rightarrow → The Mystery of Photoelectric Effect → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Time Scales
Emission Times Estimate
E a b s = Energy/unit time electron = ( U × c × Area ) ( Number of electrons ) E_{a b s}=\frac{\text { Energy/unit time }}{\text { electron }}=\frac{(U \times c \times \text { Area })}{(\text { Number of electrons })} E ab s = electron Energy/unit time = ( Number of electrons ) ( U × c × Area )
T = ϕ 0 E T=\frac{\phi_0}{\mathscr{E}} T = E ϕ 0
Monochromatic Plane Wave → \rightarrow → → \rightarrow → Time Scales → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Forced Oscillation
Time Scales
Emission Times Estimate
E a b s = Energy/unit time electron = ( U × c × Area ) ( Number of electrons ) E_{a b s}=\frac{\text { Energy/unit time }}{\text { electron }}=\frac{(U \times c \times \text { Area })}{(\text { Number of electrons })} E ab s = electron Energy/unit time = ( Number of electrons ) ( U × c × Area )
T = ϕ 0 E T=\frac{\phi_0}{\mathscr{E}} T = E ϕ 0
The Mystery of Photoelectric Effect → \rightarrow → → \rightarrow → Forced Oscillation → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Emission Time
Numerical Estimate
Relevant Data
Material
Sodium
Work function
2.36 e V 2.36 \mathrm{eV} 2.36 eV
Number of Electrons
10 19 10^{19} 1 0 19
Wavelength
300 − 400 n m 300-400 \mathrm{~nm} 300 − 400 nm
Intensity
≈ 10 − 6 W / m 2 \approx 10^{-6} \mathrm{~W} / \mathrm{m}^2 ≈ 1 0 − 6 W / m 2
Energy/Atom
≈ 10 − 25 W \approx 10^{-25} \mathrm{~W} ≈ 1 0 − 25 W
Time taken for emission
≈ 2.6 × 10 6 s \approx 2.6 \times 10^6 \mathrm{~s} ≈ 2.6 × 1 0 6 s
Time Scales → \rightarrow → → \rightarrow → Emission Time → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Example
24 × 3600 × 30 24 \times 3600 \times 30 24 × 3600 × 30
= 2.6 × 10 6 seconds =2.6 \times 10^6 \text { seconds } = 2.6 × 1 0 6 seconds
6400 k m 6400 km 6400 km
6.4 × 10 6 m 6.4 \times 10^6 m 6.4 × 1 0 6 m
10 − 9 s 10^{-9} s 1 0 − 9 s
Forced Oscillation → \rightarrow → → \rightarrow → Example → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Ordinary Units
Comparisons
Time required for Emission: ≈ \approx ≈
Real Time Required: 10 − 9 s 10^{-9} \mathrm{s} 1 0 − 9 s
Discrepancy: 10 15 10^{15} 1 0 15
The Earth-Sun Distance: 10 11 m 10^{11} \mathrm{m} 1 0 11 m
Size of a dust particle: 10 − 5 − 10 − 6 m 10^{-5}-10^{-6} \mathrm{m} 1 0 − 5 − 1 0 − 6 m
Emission Time → \rightarrow → → \rightarrow → Ordinary Units → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Crisis in Physics
Experiments and Experiments
Wave Nature of electromagnetic radiation has solid experimental support
Laws of reflection and refraction (Fresnel)
Diffraction
interference
(1) Young double slit (Visible region - Light)
(2) Hertz and J C Bose (microwave)
J C Bose and Marconi (Radio Waves)
Example → \rightarrow → → \rightarrow → Crisis in Physics → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 A particle interpretation
Is there a Way Out?
The 1905 Revolution
Albert Einstein
Ordinary Units → \rightarrow → → \rightarrow → A particle interpretation → \rightarrow → → \rightarrow → E = h ν E = h \nu E = h ν
Photoelectric Effects Facts And Prospects L-2 Prehistory Black Body Radiation
Crisis in Physics → \rightarrow → → \rightarrow → Prehistory Black Body Radiation → \rightarrow → E = h ν E = h \nu E = h ν → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 New Physics E = h ν E = h \nu E = h ν
Light can also exhibit Particle like properties
I ( ν , T ) = 2 h ν 3 c 2 1 e x p h ν k T − 1 ⟶ ( 1 ) I(\nu, T) = \frac{2h\nu^3}{c^2} \frac{1}{exp \frac{h\nu}{kT}-1}\longrightarrow (1) I ( ν , T ) = c 2 2 h ν 3 e x p k T h ν − 1 1 ⟶ ( 1 )
Two limits: h → 0 h \rightarrow 0 h → 0 T → ∞ T \rightarrow \infty T → ∞
I ( ν , T ) → 2 ν 2 c 2 k T ⟶ ( 2 ) I(\nu, T) \rightarrow \frac{2 \nu^2}{c^2 k T} \longrightarrow (2) I ( ν , T ) → c 2 k T 2 ν 2 ⟶ ( 2 )
A particle interpretation → \rightarrow → → \rightarrow → New Physics E = h ν E = h \nu E = h ν → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Planck Hypothesis
Prehistory Black Body Radiation → \rightarrow → E = h ν E = h \nu E = h ν → \rightarrow → Planck Hypothesis → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Radiation
New Physics E = h ν E = h \nu E = h ν → \rightarrow → → \rightarrow → Radiation → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 The Planck Solution
New Physics: E = h ν E = h \nu E = h ν
Light can also exhibit Particle like properties
I ( ν , T ) = 2 h ν 3 c 2 1 e x p h ν k T − 1 ⟶ ( 1 ) I(\nu, T) = \frac{2h\nu^3}{c^2} \frac{1}{exp \frac{h\nu}{kT}-1}\longrightarrow (1) I ( ν , T ) = c 2 2 h ν 3 e x p k T h ν − 1 1 ⟶ ( 1 )
Two limits: h → 0 h \rightarrow 0 h → 0 T → ∞ T \rightarrow \infty T → ∞
I ( ν , T ) → 2 ν 2 c 2 k T ⟶ ( 2 ) I(\nu, T) \rightarrow \frac{2 \nu^2}{c^2 k T} \longrightarrow (2) I ( ν , T ) → c 2 k T 2 ν 2 ⟶ ( 2 )
Planck Hypothesis → \rightarrow → → \rightarrow → The Planck Solution → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 The Einstein Revolution
Take the photon concept seriously
Radiation of frequency ν \nu ν h ν h \nu h ν
Radiation → \rightarrow → → \rightarrow → The Einstein Revolution → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Marriage of Incompatibles
The Planck Solution → \rightarrow → → \rightarrow → Marriage of Incompatibles → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Classical- Quantum
The Einstein Revolution → \rightarrow → → \rightarrow → Classical- Quantum → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 The Planck Hypothesis
Marriage of Incompatibles → \rightarrow → → \rightarrow → The Planck Hypothesis → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Two Simple but Radical Assumptions
The incident radiation of frequency ν \nu ν h ν h \nu h ν
Electrons in the metal escape to free space by transfer of energy from an individual photon
Energy is strictly conserved in this process
Maximum kinetic energy corresponds to complete absorption of photon
Classical- Quantum → \rightarrow → → \rightarrow → Two Simple but Radical Assumptions → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Collision
Collision between individual photon & Electron
The Planck Hypothesis → \rightarrow → → \rightarrow → Collision → \rightarrow → → \rightarrow →
Photoelectric Effects Facts And Prospects L-2 Thank You
Two Simple but Radical Assumptions → \rightarrow → → \rightarrow → Thank You → \rightarrow → → \rightarrow →
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Photoelectric Effects Facts And Prospects L-2 Photoelectric Effects Facts and Prospects $\rightarrow$ $\rightarrow$ Photoelectric Effects Facts and Prospects $\rightarrow$ Photo electric Effect Time Line $\rightarrow$ 1905- Annus Mirabilis(The Miraculous Year)
