intro
Question 1:
Which statement below accurately describes the effect of increasing light intensity on photoelectric current?
Topic: Photoelectric Effect
Correct Answer: A) It increases the current.
- The photoelectric effect refers to the emission of electrons when light is shone onto a material.
- The intensity of light is directly proportional to the photoelectric current, as increasing the intensity results in more electrons being emitted, thus increasing the current.
- The stopping voltage remains the same regardless of the light intensity, and it is determined by the energy of the incoming photons, not the number.
Question 2:
Which of the following phenomena cannot be justified by the wave theory of light?
Topic: Wave Theory of Light
Correct Answer: B) Photoelectric effect
- The wave theory of light explains phenomena like reflection, polarization, and interference.
- However, it falls short when attempting to explain the photoelectric effect, which suggests that light energy is quantized into discrete packets or "photons."
- So, the correct answer is B) "Photoelectric effect."
Question 3:
In Einstein's photoelectric equation, what does the graph of the photoelectron's kinetic energy versus the incident radiation frequency look like?
Topic: Einstein's Photoelectric Equation
Correct Answer: D) Graph D
- Einstein's photoelectric equation describes the relationship between the kinetic energy of ejected photoelectrons and the frequency of the incident radiation.
- The graph is a straight line with a positive slope, starting from the threshold frequency on the x-axis (frequency of incident radiation).
- So, the correct answer is D) "Graph D."
Question 4:
To facilitate pair production, the energy of the photon (hf) should be:
Topic: Pair Production
Correct Answer: C) Greater than 2moc²
- Pair production is a phenomenon where a photon, passing near a nucleus, converts its energy into a particle-antiparticle pair, usually an electron and its antiparticle, the positron.
- The energy of the photon (hf) must be at least equal to the total rest energy of the two particles, expressed as 2moc², in order to facilitate this transformation.
- Therefore, the correct answer is C) "Greater than 2moc²," indicating the minimum energy requirement for pair production.
Question 5:
Which phenomena demonstrate both the particle and wave nature of electromagnetic waves and electrons?
Topic: Duality of Electromagnetic Waves and Electrons
Correct Answer: D) The photoelectric effect and electron microscopy
- The photoelectric effect and electron microscopy are two phenomena that exhibit the duality of electromagnetic waves and electrons, showing both particle and wave nature.
- The photoelectric effect involves the emission of electrons (particles) when light (an electromagnetic wave) strikes a material.
- In electron microscopy, a beam of electrons is used to illuminate a specimen and create an image, demonstrating the wave-like nature of electrons through behaviors like interference and diffraction.
Question 6:
When the wavelength of light in beam "A" is double the wavelength of light in beam "B," how does the energy of a photon in beam "A" compare?
Topic: Energy and Wavelength of Photons
Correct Answer: A) Half the energy of a photon in beam B
- The energy of a photon is inversely proportional to its wavelength according to the Planck-Einstein relation: E = hc/λ.
- If the wavelength of light in beam "A" is twice that in beam "B," then the energy of a photon in beam "A" is half that in beam "B."
Question 7:
Which of the following phenomena demonstrate the particle nature of light?
Topic: Particle Nature of Light
Correct Answer: D) Photoelectric effect
- The photoelectric effect is a primary demonstration of the particle nature of light.
- In the photoelectric effect, electrons are emitted from a material when it is exposed to light of sufficient frequency, suggesting that light is made up of discrete packets, or "photons."
Question 8:
How does a decrease in the wavelength of incident radiation in photoemission affect the kinetic energy of photoelectrons?
Topic: Photoemission and Kinetic Energy
Correct Answer: D) It increases the maximum kinetic energy of photoelectrons
- In the photoemission process, electrons are ejected from a material when exposed to incident radiation.
- The kinetic energy of photoelectrons is influenced by the frequency of the incident radiation, which is inversely proportional to the wavelength.
- As the wavelength of the incident radiation decreases, its frequency increases, leading to an increase in the maximum kinetic energy of the photoelectrons.
MCQ 9:
Which law states that the energy radiated is directly proportional to the fourth power of the temperature in Kelvins?
Topic: Radiated Energy and Temperature
Correct Answer: C) Stefan's law
- Stefan's law, also known as the Stefan-Boltzmann law, outlines the relationship between the total radiant energy emitted by a surface and its temperature.
- This law states that the total radiant energy is directly proportional to the fourth power of the temperature measured in Kelvins.
- Therefore, the correct answer to this question is C) "Stefan's law."
MCQ 10:
Under what conditions does the Compton shift equal the Compton wavelength?
Topic: Compton Scattering and Wavelength Shift
Correct Answer: D) When scattered X-rays are observed at θ = 90°
- The Compton effect, or Compton scattering, describes the interaction between an X-ray photon and a loosely bound electron.
- The Compton shift refers to the change in wavelength of the scattered photon, while the Compton wavelength is a constant based on Planck's constant and the speed of light.
- The Compton shift equals the Compton wavelength when the scattering angle (θ) of the X-rays is 90°.
- Therefore, the correct answer is D) "When scattered X-rays are observed at θ = 90°."
Question 11:
What is the consequence of γ-ray photons interactions?
Topic: γ-ray Photons and Their Effects
Correct Answer: C) They lead to Pair production
- γ-ray photons, which are high-energy photons, interact with matter in several ways, one of which is pair production.
- Pair production is a phenomenon where a particle and its antiparticle are created from the photon's energy.
- Hence, the correct response is C) "They lead to Pair production."
Question 12:
Consider a light source positioned 10 cm from a photocell, inducing a stopping potential of Vo. What happens to the stopping potential if the light source is moved to a distance of 20 cm?
Topic: Photocell and Stopping Potential
Correct Answer: D) It remains Vo
- The stopping potential in a photocell setup is the minimum electric potential required to stop photoelectrons, and it is independent of the distance between the light source and the photocell.
- Even if the light source is moved further away, the stopping potential will remain the same because it's determined by the energy of the incident light, not its intensity.
- Therefore, the correct answer is D) "It remains Vo."
Question 13:
Which phenomenon provides the most compelling evidence for the wave nature of matter?
Topic: Wave Nature of Matter
Correct Answer: D) The diffraction of electrons by crystals
- The wave nature of matter is a fundamental concept in quantum mechanics, demonstrated by several key experiments.
- The diffraction of electrons by crystals, as revealed in the Davisson-Germer experiment, provides direct evidence of matter behaving like waves.
- This phenomenon, where electrons exhibit wave-like properties when they interact with a crystal lattice, supports the wave-particle duality of matter.
- Therefore, the correct answer is D) "The diffraction of electrons by crystals."
Question 14:
Regarding J. J. Thompson's experimental findings for electrons, what do these demonstrate?
Topic: Particle Nature of Electrons
Correct Answer: C) The particle-like behavior of matter
- J. J. Thompson's experiment, which calculated the charge-to-mass ratio of electrons, required the assumption of particle-like characteristics in electrons.
- This experiment provided key insights into the particle nature of matter.
- Therefore, the appropriate response is C) "The particle-like behavior of matter."
Question 15:
The concept of matter behaving as waves was proposed by whom?
Topic: De Broglie Hypothesis
Correct Answer: B) de-Broglie
- The concept of matter waves, i.e., particles of matter displaying wave-like behavior, was introduced by Louis de Broglie.
- This idea, now known as de Broglie's hypothesis, is a fundamental pillar in the field of quantum mechanics.
- Therefore, the correct response is B) "de-Broglie."
Question 16:
For a particle with mass "m" and de-Broglie wavelength "λ", what is the velocity?
Topic: De Broglie Wavelength and Particle Velocity
Correct Answer: A) h/mλ
- The de Broglie wavelength of a particle is used to describe its wave-like properties according to quantum mechanics.
- The relationship between the de Broglie wavelength (λ), mass (m), and velocity of a particle is given by the formula: v = h/mλ, where 'h' is Planck's constant.
- Therefore, the correct answer is A) "h/mλ."
Question 17:
Which experiment provides concrete evidence for the wave characteristics of particles?
Topic: Confirmation of Wave Nature in Particles
Correct Answer: D) The results of the Davisson and Germer experiment
- The wave characteristics of particles, a central principle in quantum mechanics, is evident through a number of key experiments.
- The Davisson and Germer experiment, in particular, offers substantial evidence of the wave nature of particles.
- This experiment showed that electrons behave like waves when they interact with a crystalline structure, confirming the wave-particle duality principle.
- Hence, the correct answer is D) "The results of the Davisson and Germer experiment."
MCQs 18:
If ultraviolet radiation of 6.2 eV strikes an aluminium surface with a work function of 4.2 eV, what will be the kinetic energy (in joules) of the most energetic electron?
Topic: Photoelectric Effect and Kinetic Energy of Electrons
Correct Answer: D) 3×10-19 J
- The kinetic energy of emitted electrons from a surface struck by radiation can be calculated by subtracting the work function from the energy of the incident radiation.
- In this case, the kinetic energy of the most energetic electron would equal the energy of the ultraviolet radiation (6.2 eV) minus the work function of aluminium (4.2 eV), which is equal to 2 eV.
- Converting this energy value to joules gives approximately 3×10-19 J.
- Therefore, the correct answer is D) "3×10-19 J."
MCQs 19:
In the photoelectric effect, what characteristic does light exhibit?
Topic: Nature of Light in the Photoelectric Effect
Correct Answer: C) Particle nature
- The photoelectric effect is a phenomenon that offers conclusive evidence of the particle nature of light.
- It is only when assuming that light is composed of individual packets of energy, known as photons, that the photoelectric effect can be adequately explained. Each photon is absorbed by a single electron.
- This absorption leads to the emission of electrons, demonstrating the particle-like behavior of light.
- Thus, the correct answer is C) "Particle nature."
MCQs 20:
Considering an electron and a proton that exhibit wave-like behavior with identical wavelengths, what corresponds to them being the same?
Topic: Momentum and Wavelength
Correct Answer: B) Momentum
- According to De Broglie's hypothesis, particles such as electrons and protons can exhibit wave-like behavior, with their wavelengths connected to their momentum through the relationship λ = h/p, where 'h' is Planck's constant.
- If two particles (in this case, an electron and a proton) have the same wavelength, then their momenta must also be the same, since 'h' is a universal constant.
- Therefore, the correct answer is B) "Momentum."
- This result demonstrates the wave-particle duality at work in quantum mechanics - a particle can exhibit both wave and particle properties depending on the circumstances in which it is observed.
MCQs 21:
What is the rest mass of a photon?
Topic: Rest Mass of Photons
Correct Answer: C) Zero
- Photons, the quantum of electromagnetic radiation, possess energy and momentum but no resting mass.
- This is a distinctive characteristic of photons as particles of light, as opposed to other particles such as electrons or protons which have a rest mass.
- Therefore, when at rest, the mass of a photon is considered zero.
- As a result, the correct answer is C) "Zero."
MCQs 22:
What are the units of h/moc?
Topic: Units of Compton Wavelength
Correct Answer: A) m
- The term 'h/moc' refers to Compton wavelength, where 'h' is Planck's constant, 'mo' is the rest mass of a particle, and 'c' refers to the speed of light.
- The units of 'h' are Joule-seconds (J.s), 'mo' is in kilograms (kg), and 'c' is in meters per second (m/s).
- As a result, The units of 'h/moc' will be meters (m).
- Therefore, the correct answer is A) "m."
MCQs 23:
Which traits do both radiation and matter display?
Topic: Dual Nature of Radiation and Matter
Correct Answer: A) Wave and particle characteristics
- One of the fundamental concepts of quantum physics is the wave-particle duality, which suggests that all quantum entities exhibit both wave and particle properties.
- Accordingly, both radiation (such as light) and matter possess characteristics associated with waves (such as interference and diffraction) and particles (such as localization and momentum).
- This dual nature is encapsulated in theories such as the De Broglie hypothesis and Heisenberg's uncertainty principle.
- Thus, the correct response is A) "Wave and particle characteristics."
MCQs 24:
Which kind of light most evidently demonstrates Compton scattering when interacting with electrons?
Topic: Compton Scattering and Electrons
Correct Answer: D) X-rays
- Compton Scattering refers to the phenomenon where X-ray or gamma-ray photons are deflected by electrons, resulting in a shift in the energy (and hence frequency) of the photon.
- This effect is most conspicuous when dealing with high-energy photons, such as X-rays or gamma rays, due to the significant energy transfer that can occur during the interaction.
- The Compton effect is a critical piece of evidence supporting the particle theory of light.
- Consequently, the correct answer is D) "X-rays."
MCQs 25:
What is the de Broglie wavelength of an object with a mass of 2 mg and a velocity of 1 m/s?
Topic: de Broglie Wavelength Calculation
Correct Answer: C) 3.3⨯10-28 m
- The de Broglie wavelength of a particle is given by λ = h/p, where 'h' is Planck's constant and 'p' is the momentum of the particle.
- To find the de Broglie wavelength, we need to substitute the given values into the formula, with mass (m) as 2 mg = 2 * 10^-6 kg and velocity (v) as 1 m/s. The momentum (p) of the particle is then mv = 2 * 10^-6 kg * 1 m/s.
- Substituting these values into the equation gives λ = 6.63⨯10^-34 J.s / 2 * 10^-6 kg * 1 m/s = 3.3⨯10^-28 m.
- Thus, the correct answer is C) "3.3⨯10^-28 m."
MCQs 26:
Which experimental evidence best supports the wave characteristics of matter?
Topic: Wave Nature of Matter
Correct Answer: A) Davisson and Germer's electron diffraction experiment
- The wave nature of matter is a crucial concept in quantum physics, which states that all particles exhibit both particle and wave-like behaviors.
- The Davisson and Germer experiment involved the diffraction of electrons, which is a wave phenomenon, thus providing direct evidence for the wave nature of matter.
- The other options, while important in the study of matter and light, do not provide direct evidence for the wave nature of matter.
- Therefore, the correct response is A) "Davisson and Germer's electron diffraction experiment."
MCQs 27:
If a particle's momentum is increased twofold, what effect does this have on its de Broglie wavelength?
Topic: Momentum and de Broglie Wavelength Relationship
Correct Answer: B) It halves
- The de Broglie wavelength of a particle is given by λ = h/p, where h is Planck's constant and p is the particle's momentum.
- From this equation, it's clear that the de Broglie wavelength is inversely proportional to the momentum. Therefore, if the momentum doubles, the de Broglie wavelength will halve.
- The other options do not reflect the inverse relationship between momentum and de Broglie wavelength.
- Thus, the correct answer is B) "It halves."
MCQ 28:
A photon with an energy of 4 eV strikes a metallic surface with a work function of 2 eV. What is the minimum reverse potential needed to halt the emission of electrons?
Topic: Photoelectric Effect and Stopping Potential
Correct Answer: A) 2 V
- The photoelectric effect demonstrates that kinetic energy of ejected electrons is given by the equation KE_max = hv - φ, where hv is the energy of the incoming photon and φ is the work function of the metal.
- When a photon with 4 eV energy strikes a metallic surface with a work function of 2 eV, the maximum kinetic energy of the emitted electrons would be 4 eV - 2 eV = 2 eV.
- The stopping potential is the reverse voltage required to stop the most energetic photoelectrons, which in this case equals to the maximum kinetic energy of the electrons.
- Therefore, the correct answer is A) "2 V."
MCQ 29:
Which phenomenon adequately demonstrates the dual nature of radiation?
Topic: Dual Nature of Radiation
Correct Answer: C) Both the photoelectric effect and diffraction
- The concept of the dual nature of radiation states that light and other forms of electromagnetic radiation can exhibit both wave-like and particle-like properties.
- The photoelectric effect illustrates the particle-like properties of light, while diffraction shows its wave-like properties.
- Other phenomena, although related to light and electromagnetic radiation, do not demonstrate both aspects concurrently.
- As a result, the correct answer is C) "Both the photoelectric effect and diffraction."
MCQ 30:
Which phenomenon best illustrates the wave-like characteristics of electrons?
Topic: Wave-like Properties of Electrons
Correct Answer: B) Diffraction by crystalline solids
- Electrons, as quantum entities, exhibit both particle and wave-like characteristics according to De Broglie's hypothesis.
- When electrons interact with crystalline solids, they display diffraction, a distinctly wave-like behavior.
- While other options involve electrons, they do not explicitly demonstrate their wave-like nature.
- The correct response is therefore B) "Diffraction by crystalline solids."
Question 31:
What is the term for indivisible, tiny energy packets in electromagnetic radiation?
Topic: Quantum Nature of Electromagnetic Radiation
Correct Answer: C) Photon
- Electromagnetic radiation is composed of discrete energy packets called photons.
- These photons carry no charge and their energy depends on their frequency.
- Therefore, the correct answer is C) "Photon."
Question 32:
What would be the threshold frequency for a metal with a work function of 3.3 eV?
Topic: Threshold Frequency and Work Function
Correct Answer: A) 8×1014 Hz
- The threshold frequency is related to the work function through φ = hν₀, where φ is the work function, h is Planck's constant, and ν₀ is the threshold frequency.
- Given the work function (3.3 eV), you can calculate the threshold frequency as 8×1014 Hz.
- Therefore, the correct answer is A) "8×1014 Hz."
Question 33:
In the Davison Germer experiment, what characteristic do diffracted protons from crystals exhibit?
Topic: Davison Germer Experiment and Wave Properties
Correct Answer: C) Wave Property
- The Davison Germer experiment provided evidence for the wave-like properties of particles, confirming the de Broglie hypothesis.
- In this experiment, protons diffracted from a crystal exhibited patterns similar to those formed by waves, demonstrating their wave properties.
- Therefore, the correct answer is C) "Wave property."
Question 34:
What is the value of the product ∆p∆x?
Topic: Uncertainty Principle
Correct Answer: C) h
- The product ∆p∆x represents the uncertainty in momentum and position of a particle, respectively.
- According to Heisenberg's uncertainty principle, ∆p∆x ≈ h, where h is Planck's constant.
- So, the correct answer is C) "h."
Question 35:
What factor is the energy of a photon directly related to?
Topic: Energy and Frequency of Photons
Correct Answer: C) Oscillation rate
- The energy of a photon is directly related to its frequency according to the equation E = hf, where h is Planck's constant and f is the frequency of the photon.
- Therefore, the correct answer is C) "Oscillation rate."