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What is the significance of Maxwell's electromagnetic wave theory in the context of quantum physics?
It explained some properties of light like interference, diffraction, and polarization, but could not address phenomena such as the spectrum of electromagnetic waves and the photoelectric effect.
What phenomenon occurs when ultraviolet light illuminates a negatively charged zinc plate?
The plate can produce an electrical discharge even at low-intensity.
What does the term 'incandescence' refer to in the context of electromagnetic radiation?
It refers to the emission of light by a hot object, particularly in the visible light range.
What is an emission spectrum?
A graph showing the intensity of radiation emitted from an object over a range of frequencies.
What relationship between temperature and frequency is noted in the context of emission spectra?
As the temperature increases, the frequency at which the maximum amount of energy is emitted also increases.
What was Max Planck's significant contribution to the understanding of emission spectra?
He proposed that atoms can only emit or absorb discrete amounts of energy.
Define the photoelectric effect.
the emission of electrons when the electromagnetic radiation falls on the object
What is the threshold frequency (fo) in photoelectric effect experiments?
The minimum frequency needed for incident radiation to eject electrons from the surface of a metal.
How does the photoelectric effect contradict classical electromagnetism?
Classical theory predicted that any frequency of light should eject electrons, regardless of intensity, which is not observed in experiments.
What is the formula for the energy of a photon?
E = hf, where E is the energy, h is Planck's constant, and f is the frequency.
What is the kinetic energy of an ejected electron based on the photoelectric effect?
KE = hf - hfo, where hf is the energy of the incident photon and hfo is the work function of the metal.
What is a photocell and how does it function in the context of the photoelectric effect?
A photocell contains two metal electrodes and measures current flow, allowing electrons ejected from the cathode to be attracted to the anode when exposed to light.
What determines the current produced in a photocell when incident light strikes the cathode?
The frequency of the incident radiation; only light above the threshold frequency will produce a measurable current.
What does Einstein's theory suggest about the interaction between photons and electrons?
One photon interacts with one electron, and an electron cannot accumulate energy from multiple lower-energy photons to escape.
What is the Compton effect?
The scattering of a photon by matter resulting in a photon of longer wavelength and lower energy.
How does the intensity of incident light relate to the number of emitted photoelectrons?
Greater intensity means more photons per second, leading to the ejection of more photoelectrons if their energy is sufficient.
What is the work function in relation to photoelectric effect?
The minimum energy required to free the most weakly bound electron from the surface of a metal.
Why can't red light produce a photoelectric effect in certain metals?
Red light does not provide enough energy (frequency) to overcome the work function for those metals.
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