Quantum Basics
Which idea states that particles can behave like both waves and solid objects?
A. Classical mechanics
B. Quantization
C. Wave–particle duality
D. Entanglement
C. Wave–particle duality
Wave-particle duality is a fundamental concept in quantum mechanics stating that all matter and energy, like electrons and photons, exhibit both wave-like and particle-like characteristics.
In the double-slit experiment, bright bands appear due to:
A. Particle collisions
B. Destructive interference
C. Constructive interference
D. Magnetic fields
C. Constructive interference
Bright fringes occur where the waves from the two slits arrive in phase, reinforcing each other through constructive interference.
What equation relates energy of a photon to its frequency?
A. p = mv
B. E = ½mv²
C. F = qE
D. E = hf
D. E = hf
The slides repeatedly show E = hf to define photon energy, linking frequency directly to energy.
The Heisenberg Uncertainty Principle relates uncertainty in:
A. Mass & charge
B. Position & momentum
C. Force & time
D. Velocity & gravity
B. Position & momentum
The uncertainty relation Δx Δp ≥ h/4π directly links the imprecision of knowing a particle’s position with its momentum.
Which device produces coherent light using stimulated emission?
A. LED
B. Laser
C. MRI
D. Diode
B. Laser
The slides described lasers as emitting coherent photons through stimulated emission, a distinctly quantum process.
What experiment first showed that single electrons can create interference patterns?
A. Stern–Gerlach experiment
B. Photoelectric experiment
C. Double-slit experiment
D. Rutherford scattering
C. Double-slit experiment
Even when electrons pass through the slits one at a time, they build up a wave-like interference pattern, proving they behave as waves until measured.
What property of light determines its color?
A. Speed
B. Frequency
C. Mass
D. Temperature
B. Frequency
Color corresponds to the frequency of photons, as shown in the slides explaining E = hf and emission spectra.
Why does hydrogen emit only specific colors?
A. Electrons move randomly
B. Energy levels are continuous
C. Electrons absorb all frequencies
D. Energy levels are quantized
D. Energy levels are quantized
Hydrogen electrons can only occupy specific energy levels, so emission occurs at exact energy (and color) differences between those levels.
According to uncertainty, if you know position very precisely, momentum becomes:
A. Zero
B. More precise
C. Impossible to define exactly
D. Easier to calculate
C. Impossible to define exactly
As position uncertainty shrinks, momentum uncertainty grows dramatically, meaning it becomes impossible to know exact momentum.
What quantum property makes MRI scans possible?
A. Entanglement
B. Electron orbits
C. Spin of nuclei
D. Photon pressure
C. Spin of nuclei
MRI relies on nuclear spin states aligning and precessing in magnetic fields, enabling imaging signals.
De Broglie wavelength depends on which quantity?
A. Charge
B. Momentum
C. Temperature
D. Mass only
B. Momentum
The de Broglie equation λ = h / p shows wavelength is inversely related to momentum, demonstrating that faster or heavier particles have smaller wavelengths.
Which of the following increases a photon’s energy?
A. Lowering frequency
B. Increasing wavelength
C. Increasing frequency
D. Adding mass
C. Increasing frequency
Photon energy increases directly with frequency according to E = hf; higher frequency means more energetic light.
If a photon’s frequency doubles, its energy:
A. Doubles
B. Halves
C. Stays the same
D. Becomes zero
A. Doubles
Energy is proportional to frequency in E = hf, so doubling f directly doubles E.
Quantum tunneling occurs because particles:
A. Gain extra energy randomly
B. Are repelled by nuclei
C. Have wavefunctions that extend through barriers
D. Emit photons as they pass barriers
C. Have wavefunctions that extend through barriers
Particles are described by wavefunctions that penetrate barriers, giving a non-zero probability of appearing on the other side.
Semiconductors function because electrons occupy:
A. Random levels
B. Continuous levels
C. Quantized energy bands
D. Gravitational states
C. Quantized energy bands
Semiconductor behavior depends on quantized valence and conduction bands that control electron flow.
Which statement best describes superposition?
A. Particles disappear when not observed
B. Particles exist in multiple possible states until measured
C. Particles always follow exact paths
D. Two particles share quantum states
B. Particles exist in multiple possible states until measured
Superposition allows particles to occupy multiple states or positions simultaneously until a measurement forces them into one definite state.
Why do electrons produce interference patterns?
A. They bounce off each other
B. They carry charge
C. They behave as waves when unobserved
D. They travel too slowly to avoid diffraction
C. They behave as waves when unobserved
Electrons have wave-like properties, so their probability waves interfere even when single electrons pass through the setup.
Which transition releases the highest-energy photon?
A. Small drop between close levels
B. A large drop between widely spaced levels
C. No drop at all
D. A sideways transition
B. A large drop between widely spaced levels
Larger energy-level differences (ΔE) emit higher-frequency, higher-energy photons, as shown in the emission diagrams.
Which phenomenon makes scanning tunneling microscopes (STM) possible?
A. Refraction
B. Tunneling
C. Nuclear fusion
D. Thermal motion
B. Tunneling
STM devices operate by measuring tunneling current between a sharp tip and a surface, relying on the quantum tunneling effect.
Quantum computing gains power because qubits can exist in:
A. Only two states
B. Randomized positions
C. Superposition of states
D. Only classical bits
C. Superposition of states
Qubits can hold multiple possible states at once via superposition, giving exponential computational power.
Which principle explains why electrons do NOT orbit the nucleus like planets?
A. Newton’s First Law
B. Pauli Exclusion Principle
C. Heisenberg Uncertainty Principle
D. Coulomb’s Law
C. Heisenberg Uncertainty Principle
The Heisenberg Uncertainty Principle prevents electrons from having both a precise position near the nucleus and a well-defined momentum, eliminating the idea of fixed planetary orbits.
If an electron’s wavelength decreases, what must have increased?
A. Frequency only
B. Momentum
C. Energy level spacing
D. Its charge
B. Momentum
A smaller de Broglie wavelength means the momentum (mv) has increased, since λ = h / p shows an inverse relationship.
What determines the color of light emitted from an LED?
A. Voltage
B. Speed of electrons
C. Band gap energy
D. Shape of the diode
C. Band gap energy
The LED color corresponds to the semiconductor’s band-gap energy—the energy released when electrons transition between bands.
Entangled particles:
A. Lose all energy
B. Have identical mass
C. Share a linked quantum state
D. Move at the same speed
C. Share a linked quantum state
Entangled particles share one connected quantum state, so measuring one instantly determines the state of the other.
Quantum simulation is powerful because it allows computers to:
A. Create artificial atoms
B. Model quantum systems using quantum rules directly
C. Increase speed of classical processors
D. Replace electrons with photons
B. Model quantum systems using quantum rules directly
Classical computers struggle to simulate quantum interactions, but quantum simulators behave like the systems they model, making the process exponentially more efficient.