2A4 Basic Quantum Physics Flashcards
Explore the wave-particle duality of matter and electromagnetic energy,
What is wave-particle duality?
The concept that light and all particles can be described as both a particle and a wave.
For example, light can act as a wave (diffraction) or as particles (photons).
Define:
Photon
A massless particle that carries light energy.
## Footnote
They are massless particles that travel at the speed of light in a vacuum and belong to the class of boson particles.
Define:
Electromagnetic radiation
A form of energy that travels through space as oscillating electric and magnetic fields.
Electromagnetic radiation includes light, radio waves, and X-rays, and it propagates at the speed of light in a vacuum.
Define:
Electromagnetic spectrum
The full range of electromagnetic radiation, sorted by wavelength or frequency.
Each type differs in energy and applications.
How does wave-particle duality connect matter and electromagnetic radiation?
Both matter and electromagnetic radiation exhibit wave-like and particle-like behaviors.
Electromagnetic radiation (like light) behaves as waves in diffraction and interference, but as particles (photons) in the photoelectric effect. Matter, such as electrons, also shows wave-like behavior in experiments like diffraction.
Fill in the blank:
The energy of a photon is directly proportional to its ________.
frequency
Higher frequency corresponds to higher energy, as described by E=hν.
What is the relationship between wavelength and frequency?
They are inversely related.
A higher frequency means shorter wavelength, and vice versa. The relationship is represented as c = λ * f, where λ represents the wavelength and f represents frequency.
What is the significance of Planck’s constant in quantum physics?
It relates the energy of a photon to its frequency:
E=hv
h (Planck’s constant) is a fundamental constant in quantum mechanics. It respresents 6.62607015 × 10-34 m2 kg / s
Who proposed the idea of wave-particle duality for electrons?
Louis de Broglie
He suggested that particles like electrons have a wavelength, described by λ = h/p, whwere p is momentum.
How does the wave-particle duality relate to the development of quantum mechanics?
Electrons & photons behave as both waves and particles, forming a core principle of quantum mechanics.
## Footnote
This dual behavior was demonstrated in experiments like electron diffraction and the photoelectric effect, challenging classical physics.
What is the relationship between the wavelength of light and its energy?
Energy is inversely proportional to wavelength.
Shorter wavelengths have higher energy (E=hc/λ).
Which experiment proved the wave nature of light?
The Double Slit Experiment
This experiment, conducted by Thomas Young, showed interference patterns.
True or false:
Young’s double-slit experiment, originally for light, was later replicated with electrons to show wave-particle duality.
True
This demonstrated that even particles like electrons can create interference patterns, behaving as waves.
Fill in the blank:
Isaac Newton proposed that light is made of particles, while Christian Huygens suggested that light behaves as a _____.
wave
Newton’s particle theory explained reflection and refraction, while Huygens’ wave theory accounted for phenomena like diffraction and interference.
What is the phenomenon where light bends around obstacles or spreads after passing through a narrow slit?
Diffraction
Diffraction demonstrates the wave nature of light, as it cannot be explained by particle behavior alone.
Fill in the blanks:
Newton’s particle theory failed to explain _______ and _______, supporting the wave theory.
diffraction; interference
These phenomena involve the bending and overlapping of light waves, which cannot be accounted for by a purely particle-based theory.
True or false:
The concept of wave-particle duality explains why particles can interfere with each other, similar to waves.
True
Quantum mechanics uses the wave-particle duality to explain phenomena such as interference patterns observed in the double-slit experiment with particles like electrons.
What phenomenon, observed in the Compton scattering experiment, provided evidence for light’s particle nature?
A decrease in wavelength when X-rays scatter off electrons.
Arthur Compton showed photons transfer momentum to electrons, supporting wave-particle duality.
Fill in the blank:
Electromagnetic energy travels at the speed of _______ in a vacuum.
light
3×108 m/s2 is the universal speed limit for electromagnetic waves.
Which type of electromagnetic radiation is considered the least dangerous?
Radio waves
Radio waves have the longest wavelength and lowest frequency in the Electromagnetic spectrum.
Fill in the blanks:
The visible spectrum ranges from approximately ____ nm (violet) to ____ nm (red).
400 nm to 700 nm
The visible spectrum represents the small portion of the electromagnetic spectrum detectable by the human eye.
What type of electromagnetic radiation is used in medical imaging to view bones?
X-rays
X-rays have high energy and short wavelengths, allowing them to penetrate soft tissues but not dense materials like bones.
What kind of electromagnetic waves are commonly used in communication technologies, such as television and radio?
Radio waves
Their long wavelengths and low frequencies make them suitable for transmitting signals over long distances.
Fill in the blanks:
Gamma rays are the most energetic form of electromagnetic radiation and are produced by ______ _______.
Nuclear reactions
or radioactive decay
Gamma rays have extremely short wavelengths and high energy, making them useful in cancer treatments and astrophysics.
Which type of radiation is responsible for sunburns and can also help the body produce vitamin D?
Ultraviolet (UV) radiation
UV radiation has higher energy than visible light but can damage skin cells with overexposure.
True or false:
Microwaves are used in radar systems and to heat food by causing water molecules to vibrate.
True
Microwaves interact with water and fat molecules, generating heat in materials with these components.
Define:
Photoelectric effect
The emission of electrons from a material when it absorbs light of sufficient energy.
This phenomenon is essential for the operation of devices like solar panels.
True or false:
The photoelectric effect demonstrates the particle nature of light.
True
The ejection of electrons from a surface occurs because light delivers energy in discrete quanta (photons).
Who proposed the theory of the photoelectric effect?
Albert Einstein
Einstein’s theory was published in 1905 in his paper titled ‘On a Heuristic Point of View Concerning the Production and Transformation of Light.’
How did J.J. Thomson contribute to the study of the photoelectric effect?
He demonstrated that the particles emitted in the photoelectric effect were electrons.
His experiments with cathode rays led to the discovery of the electron and its behavior in various processes.
True or false:
Increasing the intensity of light increases the kinetic energy of ejected electrons in the photoelectric effect.
False
The energy of ejected electrons depends on the frequency of light, not its intensity.
What did Philipp Lenard discover about the photoelectric effect?
He found that the energy of emitted electrons depends on the frequency of light, not its intensity.
Lenard’s experiments laid the groundwork for Einstein’s quantum explanation.
Fill in the blank:
In the photoelectric effect, photons transfer _______ to electrons.
energy
The energy must exceed the material’s work function to eject electrons.
What does work function mean in the photoelectric effect?
The minimum energy needed to eject an electron from a material’s surface.
Light with frequency below the threshold cannot cause electron emission.
What aspect of light does the photoelectric effect contradict about classical physics?
Classical physics wrongly assumed intensity, not frequency, controls ejection.’
## Footnote
The photoelectric effect shows that this is not true. Quantum mechanics resolved this contradiction by introducing the concept of photons.
How does the photoelectric effect support the principles of quantum mechanics?
The photoelectric effect demonstrates that light behaves as quanta of energy (photons), supporting the idea that energy is quantized.
This concept, introduced by Planck and Einstein, is a cornerstone of quantum mechanics, contrasting with the classical wave theory of light.
True or false:
The photoelectric effect helped establish the idea that energy is emitted and absorbed in discrete packets, not continuously.
True
Einstein’s explanation of the photoelectric effect provided evidence for the quantization of energy, a key principle in quantum mechanics.
What range of the electromagnetic spectrum can cause the photoelectric effect in most materials?
Ultraviolet and higher frequencies.
These frequencies have sufficient energy to overcome most work functions.
True or false:
The photoelectric effect supports the wave model of light.
False
It supports the particle model by showing light delivers energy in discrete photons.
Fill in the blank:
The photoelectric effect supports the idea that electromagnetic radiation is made of discrete packets of energy called ______.
photons
This concept was key to the development of quantum mechanics.
What is the threshold frequency in the photoelectric effect?
The minimum frequency of light required to eject electrons from a material’s surface.
Light below this frequency will not cause electron emission, regardless of intensity.
True or false:
Increasing the intensity of light above the threshold frequency will increase the number of emitted electrons.
True
While intensity does not affect the energy of electrons, it increases the number of photons hitting the surface.
True or false:
Infrared light cannot trigger the photoelectric effect.
True
Infrared photons generally lack the energy needed to dislodge electrons, as their energy is below the threshold frequency required for the photoelectric effect.
How did Heinrich Hertz’s experiments contribute to the discovery of the photoelectric effect?
He observed that UV light enhanced electric sparks between metal electrodes, providing the first evidence of the photoelectric effect.
Hertz’s experiments involved a source of electromagnetic radiation and a receiver that generated a spark.
What is the purpose of photoelectron spectroscopy (PES)?
To identify the elements that make up a material by measuring ejected electron energy.
This involves shining a monochromatic X-ray at the material.
How does nuclear medicine utilize the photoelectric effect?
By using radiation to destroy cancer cells and shrink tumors.
Typically, X-rays or gamma rays are employed in this treatment. Photoelectric effect helps in imaging & radiation therapy.
True or false:
The photoelectric effect is used in night vision devices.
True
Night vision devices amplify low-intensity light by converting photons into electrons using the photoelectric effect.
How is the photoelectric effect used in astronomy?
In photoelectric photometers, which measure the intensity of starlight.
This helps astronomers study the properties of stars and other celestial objects.
What device uses the photoelectric effect to convert sunlight into electricity?
Solar panels
(photovoltaic cells)
These cells convert light into electrical energy, a practical application of the photoelectric effect.
What role does the photoelectric effect play in photoelectric sensors?
It detects light and converts it into an electrical signal.
These sensors are used in automatic doors, burglar alarms, and other devices.
