AP Physics 2:: Quantum Atomic Nuclear

What is a PHOTON, and what does it represent about the nature of LIGHT, specifically regarding light's ability to behave as discrete PACKETS of energy rather than a purely continuous wave?

- **A)** This concept has no actual relationship between photons and light's ability to behave as discrete energy packets
- **B)** A photon is a discrete 'packet' (quantum) of electromagnetic energy; the existence of photons demonstrates that light can behave as PARTICLE-LIKE, discrete units of energy, complementing (not replacing) its well-established WAVE-like behavior (from the earlier Optics unit)
- **C)** Photons demonstrate that light behaves ONLY as particles, with NO wave-like properties whatsoever, contradicting the interference phenomena discussed in the earlier Optics unit
- **D)** A photon is identical to an electron, with no actual distinction between these two types of particles

What is the mathematical FORMULA for the ENERGY of a single PHOTON, in terms of its FREQUENCY, using Planck's constant?

- **A)** This concept has no actual mathematical relationship between a photon's energy and its frequency
- **B)** A photon's energy is INVERSELY proportional to its frequency, meaning HIGHER frequency photons carry LESS energy -- the reverse of the actual relationship
- **C)** E = h*f, where h is PLANCK'S CONSTANT (a very small, fundamental constant) and f is the photon's frequency -- a HIGHER frequency photon carries MORE energy
- **D)** E = h/f (dividing by frequency), rather than multiplying by it

What is the PHOTOELECTRIC EFFECT, and what OBSERVATION (light ejecting ELECTRONS from a metal surface) does this phenomenon describe?

- **A)** The photoelectric effect is the EMISSION of electrons from a metal surface when light of SUFFICIENT energy (frequency) shines on it -- the incoming light's energy is transferred to electrons within the metal, and if that energy is enough to overcome the metal's binding forces, electrons are EJECTED from the surface
- **B)** The photoelectric effect occurs only in the COMPLETE ABSENCE of light, with no actual relationship to light exposure
- **C)** This concept has no actual relationship between light shining on a metal surface and the emission of electrons
- **D)** The photoelectric effect describes electrons being ABSORBED into a metal surface when light shines on it, the reverse of the actual electron-ejection phenomenon

What is the WORK FUNCTION of a metal, and what does it represent in terms of the MINIMUM energy required to eject an electron from that metal's surface via the photoelectric effect?

- **A)** The work function represents the MAXIMUM possible energy an ejected electron could ever have, rather than the minimum energy needed to eject it in the first place
- **B)** This concept has no actual relationship between a metal's work function and the minimum photon energy needed to eject an electron
- **C)** The work function (usually denoted phi) is the MINIMUM amount of energy needed to remove (eject) an electron from a specific metal's surface -- if an incoming photon's energy is LESS than the work function, NO electron will be ejected, REGARDLESS of the light's intensity (brightness)
- **D)** The work function depends only on the incoming light's INTENSITY, with no actual relationship to the specific metal's properties

Why does the PHOTOELECTRIC EFFECT'S observed THRESHOLD FREQUENCY behavior (below which NO electrons are ejected, REGARDLESS of light intensity) provide STRONG EVIDENCE for light's PARTICLE-LIKE (photon) nature, rather than being explainable by a purely classical WAVE model of light?

- **A)** A classical WAVE model would predict that even LOW-frequency light, if made sufficiently INTENSE (bright), should eventually eject electrons (since wave energy could accumulate over time) -- but this is NOT observed; instead, the PHOTON model correctly predicts that each individual photon must have ENOUGH energy (E=hf) on its OWN to eject an electron, explaining the sharp threshold frequency behavior
- **B)** The classical wave model perfectly explains the threshold frequency behavior, with no actual need for a particle-based (photon) explanation
- **C)** This concept has no actual relationship between the threshold frequency observation and evidence for light's particle-like nature
- **D)** Light intensity has no actual relationship to whether electrons are ejected via the photoelectric effect, regardless of frequency

What is the mathematical FORMULA (based on the photoelectric effect) relating the MAXIMUM KINETIC ENERGY of an ejected photoelectron to the incoming photon's energy and the metal's work function?

- **A)** This concept has no actual mathematical relationship between an ejected electron's kinetic energy, the photon's energy, and the metal's work function
- **B)** KE_max = hf + phi (adding rather than subtracting the work function), rather than the correct subtraction
- **C)** KE_max = hf - phi, where hf is the incoming photon's energy and phi is the metal's work function -- the ejected electron's maximum kinetic energy equals the photon's energy MINUS the energy required just to free the electron from the metal
- **D)** KE_max depends only on the metal's work function, with no actual dependence on the incoming photon's energy

According to the photoelectric equation KE_max=hf-phi, how does INCREASING the INTENSITY (brightness) of incoming light (WITHOUT changing its frequency) affect the MAXIMUM KINETIC ENERGY of ejected photoelectrons, versus the NUMBER of electrons ejected?

- **A)** Increasing light intensity (at a CONSTANT frequency) does NOT change the maximum kinetic energy of ejected electrons (since KE_max depends only on frequency and the work function, not intensity) -- instead, HIGHER intensity simply means MORE photons arrive per second, ejecting a GREATER NUMBER of electrons (producing a larger current)
- **B)** Light intensity has no actual relationship to either the kinetic energy or the number of electrons ejected via the photoelectric effect
- **C)** Increasing light intensity INCREASES the maximum kinetic energy of each ejected electron, contradicting the actual frequency-only dependence in KE_max=hf-phi
- **D)** Increasing intensity DECREASES the number of electrons ejected, the reverse of the actual relationship between intensity and electron count

What is WAVE-PARTICLE DUALITY, and what does this principle state about how BOTH light AND matter (like electrons) can exhibit properties of WAVES and PARTICLES, depending on the experimental context?

- **A)** This concept has no actual relationship between light, matter, and the possibility of exhibiting both wave-like and particle-like behavior
- **B)** Wave-particle duality states that entities like light and matter (electrons, etc.) can exhibit BOTH wave-like properties (like interference and diffraction) AND particle-like properties (like discrete energy packets or localized collisions), with the observed behavior depending on the specific experimental setup used to probe it
- **C)** Wave-particle duality applies only to LIGHT, with no actual relevance to matter particles like electrons
- **D)** Wave-particle duality states that light and matter must ALWAYS behave PURELY as particles, with NO actual wave-like properties ever observed