Dual Nature Of Matter And Radiation Flashcards
What is electromagnetic radiation?
Electromagnetic radiation consists of mutually perpendicular oscillating electric and magnetic fields, both being perpendicular to the direction in which the wave and energy are travelling.
What are the characteristics of a wave?
Characteristics of a wave include frequency, wavelength, amplitude, and speed.
Define frequency and wave number associated with a wave.
Frequency is the number of oscillations per unit time, while wave number is the number of wavelengths per unit distance.
How do we define momentum of a particle?
Momentum of a particle is defined as the product of its mass and velocity (p = mv).
What is the concept of quantization of energy?
Quantization of energy refers to the idea that energy is emitted in discrete packets or quanta.
Who first proposed the idea of quantization of energy?
Planck first proposed the idea of quantization of energy.
What is the relationship described by Planck’s model for energy emission?
Energy is emitted in packets, and at higher frequencies, the energy of a packet is larger (E = nhν).
What phenomenon did Heinrich Hertz discover in 1887?
Heinrich Hertz discovered photoelectric emission.
What is the photoelectric effect?
The photoelectric effect is the emission of electrons from a metal surface when radiation of appropriate frequency is incident on it.
What is required for the photoelectric effect to occur in metals like zinc and magnesium?
Ultraviolet radiation is necessary for the photoelectric effect to occur in metals like zinc and magnesium.
What are the two ways electrical energy can be obtained from light?
- Photo-emissive effect
- Photo-voltaic effect
What is the typical experimental setup for the photoelectric effect?
An evacuated glass tube with a quartz window containing a photosensitive metal plate (emitter) and a collector plate.
What happens when the anode potential is positive in the photoelectric effect setup?
It accelerates the electrons.
What is the role of the stopping potential in the photoelectric effect?
The stopping potential indicates the maximum energy needed to prevent photoelectrons from reaching the collector.
What is the work function of a metal?
The minimum amount of energy required to remove an electron from the surface of the metal.
True or False: The maximum kinetic energy of emitted photoelectrons depends on the intensity of the incident radiation.
False.
What does the photoelectric equation relate?
It relates the energy of incident light to the kinetic energy of emitted electrons.
What is the value of Planck’s constant?
6.626 × 10^-34 J s.
Fill in the blank: The equation E = hν is known as _______.
Einstein’s relation.
What phenomenon cannot be explained by wave theory regarding the photoelectric effect?
The instantaneous emission of electrons upon incidence of light.
What is the threshold frequency in the context of the photoelectric effect?
The minimum frequency of incident radiation required to emit photoelectrons from a metal surface.
What is the relationship between maximum kinetic energy and incident frequency?
Maximum kinetic energy increases with increasing incident frequency.
What is the significance of the stopping potential V0?
It indicates the point at which the photocurrent becomes zero despite the incident radiation.
How does the saturation current depend on intensity of incident radiation?
The saturation current increases proportionally with the intensity of the incident radiation.
What is Planck’s constant and its value?
Planck’s constant is a fundamental constant used in quantum mechanics, defined as h = 6.626 × 10^-34 J s.
What does Einstein’s relation E = hν represent?
It represents the relationship between energy (E) and frequency (ν) of electromagnetic radiation.
What does Einstein’s relation indicate about energy and frequency?
Energy is directly proportional to frequency and inversely proportional to wavelength.
Fill in the blank: High frequency radiation means _______ radiation.
high energy
What are the energy values for various photon energies given in the example?
10^-12 J, 10^-15 J, 10^-18 J, 10^-21 J, 10^-24 J.
What is the formula for energy of electromagnetic radiation?
E = hν.
What is the threshold frequency for photoemission?
The minimum frequency (ν₀) required to eject electrons from a metal surface.
True or False: Electrons will be emitted if the energy gained by them is less than the work function.
False.
What does the equation KEmax = hν - φ₀ represent?
It describes the maximum kinetic energy of emitted electrons in the photoelectric effect.
Fill in the blank: Photocurrent depends on the intensity of incident radiation through the number of _______ emitted.
photoelectrons
What happens to photocurrent when the intensity of incident radiation increases?
The number of emitted photoelectrons increases, leading to a higher photocurrent.
What is the significance of the stopping potential (V₀)?
It indicates the potential required to stop the most energetic emitted electrons from reaching the collector.
What relationship does V₀ have with incident frequency (ν)?
V₀ varies linearly with incident frequency.
Fill in the blank: The energy of a photon is given by _______.
hν
What did Einstein argue about the interaction of photons with electrons?
A photon gives all its energy to an electron upon collision, and the photon ceases to exist.
What is the formula to calculate the number of photons incident per second?
N = Power / Energy of a single photon.
How does the energy of emitted electrons vary?
Electrons have different kinetic energies due to varying depths of ejection and collisions.
What is the relationship between wavelength and energy for photons?
Wavelength (in Å) × energy (in eV) ≈ 12500.
What does the Compton shift relate to?
It relates the change in wavelength of photons due to scattering with electrons.
True or False: Photons can be absorbed or created during collisions.
True.
What is the relationship between intensity and electron energy in the photoelectric effect?
Intensity affects the number of emitted electrons but not their energy.
What is a key conclusion from the experiments on the photoelectric effect?
Light behaves as packets of energy called quanta.
Fill in the blank: A photon of low frequency light will not have sufficient energy to _______ an electron.
release
What is the effect of increasing the frequency of incident light?
It increases the maximum kinetic energy of the emitted electrons.
What did Compton demonstrate about photons?
Photons have associated momentum along with the energy they carry
This was established through experiments showing that photons interact with matter.
What is the rest mass of a photon?
Zero
Photons are massless particles and always move at the speed of light.
In photon-particle collisions, what quantities are conserved?
Energy and momentum
However, the number of photons is not conserved as photons can be absorbed or created.
What is Compton shift?
The change in wavelength of scattered photons, denoted as Δλ
It depends on the scattering angle during photon-electron collisions.
What experiments demonstrate the particle nature of radiation?
Black body radiation and photoelectric effect
These phenomena can only be explained by considering radiation as consisting of photons.
What does wave-particle duality imply?
Both wave and particle characteristics are necessary to describe electromagnetic radiation
This concept applies to both light and the entire electromagnetic spectrum.
What is a photocell?
A device that converts light energy into electrical energy
It operates using the photoelectric effect and is used in various applications like light meters.
How does a photocell work?
When suitable light falls on the cathode, photoelectrons are emitted and create a photocurrent
This current can be measured and used to trigger other devices.
What did de Broglie hypothesize about matter?
Matter may also possess dual nature, exhibiting both wave and particle properties
This was based on the observed symmetry in nature.
What is the de Broglie wavelength formula?
λ = h/p
Where h is Planck’s constant and p is momentum.
What confirms the wave nature of electrons?
The Davisson and Germer experiment
It demonstrated electron diffraction patterns, similar to wave interference.
What is the significance of the Davisson and Germer experiment?
It substantiated de Broglie’s hypothesis of wave-particle duality
The experiment showed that electrons exhibit wave-like behavior.
What is the relation between kinetic energy and de Broglie wavelength for a charged particle?
λ = h / √(2mEK)
Where EK is the kinetic energy and m is the mass of the particle.
True or False: The de Broglie wavelength of larger objects like cars or humans is significant.
False
The calculated wavelengths are extremely small and not observable.
Fill in the blank: The phenomenon of light exhibiting both wave and particle characteristics is known as _______.
wave-particle duality
What defines the momentum of a photon?
p = E/c
This relationship is valid for massless particles traveling at the speed of light.
What is the formula for de Broglie wavelength?
λ = h/p
What is the value of Planck’s constant h?
6.63 × 10^-34 J s
What is the de Broglie wavelength of a car moving with a momentum of 20000 kg m/s?
3.32 × 10^-38 m
What phenomenon describes the wave-like nature of material particles?
Wave-particle duality of matter
What are the classical terms used to describe waves?
- Frequency (ω) * Wave number (k)
Why are the wavelengths associated with macroscopic particles negligible?
They are negligible compared to the size of the moving objects and the widths of their paths.
What is the significance of the de Broglie wavelength for an electron passing through a small aperture?
It is comparable to the size of the hole.
What is the de Broglie wavelength of an electron with kinetic energy of 100 eV?
1.228 Å
What effect does the wavelength of the characterizing probe have on the resolution of a microscope?
The shorter the wavelength, the better the resolution.
What is thermionic emission?
The process of emitting electrons by heating a material to high temperatures (~2000 ºC).
What is field emission?
The process of emitting electrons by applying strong electric fields (~10^6 V/m) at the surface of a metal tip.
What is photo-electron emission?
The process of emitting electrons by shining suitable frequency radiation (ultraviolet or visible) on a metal surface.
What is the primary advantage of electron microscopes over optical microscopes?
Higher resolution due to shorter wavelengths associated with electrons.
Who developed the first electron microscope and when?
Herald Ruska in 1929.
What is the relationship between stopping potential and incident wavelength in the photoelectric effect?
The stopping potential is inversely linear with the incident wavelength.
What happens to the extra energy of incident radiation in the photoelectric effect when intensity increases?
It does not change the maximum kinetic energy of the electrons.
What is the work function in the context of photoelectric effect?
The minimum energy needed to remove an electron from a material.
What is the stopping potential if the photocurrent vanishes?
It is the maximum retarding potential that prevents photoelectrons from reaching the anode.
What is the threshold wavelength for tungsten?
2.76 × 10^-5 cm
What is the energy of a photon with a frequency of 5×10^14 Hz?
3.315 × 10^-19 J (or 2.071 eV)
What is the significance of the Davisson and Germer experiment?
It demonstrated the wave nature of electrons through diffraction.
Fill in the blank: The de Broglie wavelength of an electron is _______.
λ = h/p
True or False: Electrons can behave as waves.
True
What is the typical resolution of electron microscopes compared to optical microscopes?
Several hundred times higher.
What happens to photoelectrons when radiation of wavelength greater than the threshold wavelength is incident on a metal surface?
No photoelectrons are emitted.
What is the maximum kinetic energy of photoelectrons when ultraviolet radiation of wavelength 1.80 × 10^-5 cm is incident on tungsten?
2.40 eV
What is the expected behavior of an electron at rest in relation to de Broglie wavelength?
An electron at rest does not have an associated de Broglie wavelength.
What is the significance of the wavelength being comparable to atomic dimensions in electron diffraction?
It allows for the study of atomic structures.
