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Questions and Answers
What happens when high voltage is applied across mercury vapor in a fluorescent tube?
What happens when high voltage is applied across mercury vapor in a fluorescent tube?
- Mercury atoms are excited and then return to the ground state, releasing UV photons.
- The tube's phosphorus coating absorbs UV photons.
- Fast-moving free electrons collide with the mercury atoms. (correct)
- Mercury atoms cascade down energy levels and emit visible light photons.
Which process leads to the emission of visible light photons in a fluorescent tube?
Which process leads to the emission of visible light photons in a fluorescent tube?
- Return of mercury atoms to the ground state
- Absorption of UV photons by the phosphorus coating
- Excitation of mercury electrons (correct)
- Collision of free electrons with mercury atoms
What evidence supports the existence of discrete energy levels in atoms?
What evidence supports the existence of discrete energy levels in atoms?
- Variable emission wavelengths
- Continuous emission spectra
- Line emission and absorption spectra (correct)
- Random absorption of photons
Which phenomenon states that all particles exhibit both wave and particle properties?
Which phenomenon states that all particles exhibit both wave and particle properties?
In a fluorescent tube, what role does the phosphorus coating play?
In a fluorescent tube, what role does the phosphorus coating play?
What triggers the emission of UV photons in a fluorescent tube?
What triggers the emission of UV photons in a fluorescent tube?
Why do we observe lines at discrete points in line emission and absorption spectra?
Why do we observe lines at discrete points in line emission and absorption spectra?
What property of waves do particles exhibit according to wave-particle duality?
What property of waves do particles exhibit according to wave-particle duality?
How do line emission and absorption spectra relate to discrete energy levels in atoms?
How do line emission and absorption spectra relate to discrete energy levels in atoms?
What happens to the electrons in a fluorescent tube's phosphorus coating after absorbing UV photons?
What happens to the electrons in a fluorescent tube's phosphorus coating after absorbing UV photons?
Flashcards
Excitation of mercury atoms
Excitation of mercury atoms
Electrons in mercury atoms absorb energy and jump to higher energy levels.
Emission of UV photons
Emission of UV photons
Excited mercury atoms release energy by emitting photons.
Electron excitation
Electron excitation
The process by which electrons in atoms absorb energy and jump to higher energy levels.
Line emission spectrum
Line emission spectrum
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Discrete energy levels
Discrete energy levels
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Wave-particle duality
Wave-particle duality
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Diffraction of light
Diffraction of light
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UV photon conversion
UV photon conversion
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Phosphorus coating
Phosphorus coating
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Electron de-excitation
Electron de-excitation
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Study Notes
Electromagnetic Waves
- Electromagnetic waves are classified as transverse waves.
Particle Behavior of Light
- The photoelectric effect demonstrates the particle nature of light.
Photoelectric Effect
- Occurs when light above a specific frequency shines on metal, releasing electrons known as photoelectrons.
Threshold Frequency
- Defined as the minimum frequency of light necessary for an electron to be emitted from a metal surface.
Photon Energy Calculation
- The energy of a photon can be calculated using the equation E = hf = hc/λ, where:
- E = energy
- h = Planck’s constant
- f = frequency
- c = speed of light (3 x 10^8 m/s)
- λ = wavelength
Minimum Frequency Requirement
- A photon must exceed a certain frequency for electron liberation, as its energy must surpass the work function (the energy needed to free an electron).
Effects of Higher Frequency Photon
- If a photon’s frequency is above the threshold, the electron is liberated, and any excess energy translates into the electron's kinetic energy.
Effect of Increased Light Intensity
- If photoelectric emission does not occur, increasing light intensity means more photons strike the metal, but unless the photon energy is sufficient, electron emission will not occur.
Photoelectric Equation
- The equation representing the photoelectric effect is given by:
- Planck’s constant × frequency = work function + maximum kinetic energy of emitted photoelectrons.
Work Function Definition
- The work function is the energy required to free an electron from the metallic bonds holding it within a metal.
Electron Volt Explanation
- An electron volt (eV) is defined as the kinetic energy gained by an electron when accelerated through a potential difference of 1 volt.
Conversion Between Electron Volts and Joules
- To convert between electron volts and joules, use the conversion factor: 1 eV = 1.6 x 10^-19 joules.
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