Modern Physics
Q. What is the energy of a photon emitted during the transition from n=3 to n=2 in a hydrogen atom?
A.
10.2 eV
B.
1.89 eV
C.
12.1 eV
D.
3.4 eV
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Solution
The energy of the photon can be calculated using the Rydberg formula. The transition from n=3 to n=2 emits a photon of energy approximately 1.89 eV.
Correct Answer: B — 1.89 eV
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Q. What is the energy of a photon with a frequency of 5 x 10^14 Hz?
A.
3.1 x 10^-19 J
B.
2.5 x 10^-19 J
C.
4.0 x 10^-19 J
D.
6.6 x 10^-19 J
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Solution
The energy of a photon is given by E = hf. Using h = 6.63 x 10^-34 J.s, E = 6.63 x 10^-34 * 5 x 10^14 = 3.31 x 10^-19 J.
Correct Answer: A — 3.1 x 10^-19 J
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Q. What is the energy of a photon with a frequency of 5 x 10^14 Hz? (h = 6.63 x 10^-34 J.s)
A.
3.31 x 10^-19 J
B.
1.32 x 10^-19 J
C.
2.65 x 10^-19 J
D.
4.98 x 10^-19 J
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Solution
The energy of a photon is given by E = hν. Substituting the values gives E = 6.63 x 10^-34 J.s * 5 x 10^14 Hz = 3.31 x 10^-19 J.
Correct Answer: A — 3.31 x 10^-19 J
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Q. What is the energy of a photon with a wavelength of 500 nm?
A.
3.98 eV
B.
2.48 eV
C.
1.24 eV
D.
0.62 eV
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Solution
The energy of a photon is given by E = hc/λ. Using h = 6.626 x 10^-34 J·s and c = 3 x 10^8 m/s, E = (6.626 x 10^-34)(3 x 10^8)/(500 x 10^-9) = 3.98 eV.
Correct Answer: A — 3.98 eV
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Q. What is the energy of the ground state of a hydrogen atom?
A.
-13.6 eV
B.
-3.4 eV
C.
0 eV
D.
13.6 eV
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Solution
The energy of the ground state of a hydrogen atom is -13.6 eV.
Correct Answer: A — -13.6 eV
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Q. What is the half-life of a radioactive isotope?
A.
Time taken for half of the sample to decay
B.
Time taken for the entire sample to decay
C.
Time taken for the sample to double
D.
None of the above
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Solution
The half-life is defined as the time taken for half of the radioactive sample to decay.
Correct Answer: A — Time taken for half of the sample to decay
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Q. What is the half-life of a radioactive substance if it takes 10 years for half of the substance to decay?
A.
5 years
B.
10 years
C.
20 years
D.
30 years
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Solution
The half-life is defined as the time required for half of the radioactive substance to decay, which is given as 10 years.
Correct Answer: B — 10 years
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Q. What is the half-life of a radioactive substance?
A.
The time taken for half of the substance to decay
B.
The time taken for the entire substance to decay
C.
The time taken for the substance to double
D.
The time taken for the substance to reach equilibrium
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Solution
The half-life of a radioactive substance is defined as the time taken for half of the substance to decay.
Correct Answer: A — The time taken for half of the substance to decay
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Q. What is the main application of nuclear fusion?
A.
Nuclear power plants
B.
Atomic bombs
C.
Hydrogen bombs
D.
Medical imaging
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Solution
Nuclear fusion is the process that powers hydrogen bombs and is also the process that fuels stars, including the sun.
Correct Answer: C — Hydrogen bombs
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Q. What is the main characteristic of a black body?
A.
It reflects all incident light
B.
It absorbs all incident light
C.
It emits light only at high temperatures
D.
It emits light only at low temperatures
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Solution
A black body is characterized by its ability to absorb all incident light, regardless of frequency or angle of incidence.
Correct Answer: B — It absorbs all incident light
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Q. What is the main difference between alpha and beta radiation?
A.
Charge
B.
Mass
C.
Speed
D.
Penetrating power
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Solution
Alpha particles have a much greater mass than beta particles, which are electrons or positrons.
Correct Answer: B — Mass
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Q. What is the main difference between classical and quantum mechanics?
A.
Determinism vs. probability
B.
Energy conservation
C.
Force laws
D.
Motion equations
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Solution
The main difference is that classical mechanics is deterministic, while quantum mechanics incorporates probability.
Correct Answer: A — Determinism vs. probability
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Q. What is the main difference between nuclear fission and nuclear fusion?
A.
Fission combines nuclei, fusion splits them
B.
Fission splits nuclei, fusion combines them
C.
Fission occurs in stars, fusion occurs in reactors
D.
Fission is safer than fusion
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Solution
Nuclear fission involves the splitting of a heavy nucleus into smaller nuclei, while nuclear fusion involves the combining of light nuclei to form a heavier nucleus.
Correct Answer: B — Fission splits nuclei, fusion combines them
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Q. What is the main difference between nuclear fusion and nuclear fission?
A.
Fusion combines nuclei, fission splits them
B.
Fusion splits nuclei, fission combines them
C.
Fusion occurs in stars, fission occurs in reactors
D.
Both are the same process
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Solution
The main difference is that nuclear fusion combines light nuclei to form a heavier nucleus, while nuclear fission splits a heavy nucleus into lighter nuclei.
Correct Answer: A — Fusion combines nuclei, fission splits them
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Q. What is the main product of nuclear fusion in stars?
A.
Helium
B.
Hydrogen
C.
Carbon
D.
Iron
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Solution
The main product of nuclear fusion in stars is helium.
Correct Answer: A — Helium
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Q. What is the main reason for the stability of atomic nuclei?
A.
Electromagnetic force
B.
Gravitational force
C.
Strong nuclear force
D.
Weak nuclear force
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Solution
The stability of atomic nuclei is primarily due to the strong nuclear force, which binds protons and neutrons together.
Correct Answer: C — Strong nuclear force
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Q. What is the main reason for the stability of the electron orbits in an atom?
A.
Centripetal force
B.
Electrostatic force
C.
Quantum mechanics
D.
All of the above
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Solution
The stability of the electron orbits in an atom is primarily explained by quantum mechanics.
Correct Answer: C — Quantum mechanics
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Q. What is the main reason for the stability of the nucleus in an atom?
A.
Electromagnetic force
B.
Gravitational force
C.
Strong nuclear force
D.
Weak nuclear force
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Solution
The stability of the nucleus is primarily due to the strong nuclear force, which binds protons and neutrons together.
Correct Answer: C — Strong nuclear force
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Q. What is the main reason for the stability of the nucleus?
A.
Electromagnetic force
B.
Gravitational force
C.
Strong nuclear force
D.
Weak nuclear force
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Solution
The stability of the nucleus is primarily due to the strong nuclear force, which binds protons and neutrons together.
Correct Answer: C — Strong nuclear force
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Q. What is the majority charge carrier in a P-type semiconductor?
A.
Electrons
B.
Holes
C.
Neutrons
D.
Protons
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Solution
In a P-type semiconductor, holes are the majority charge carriers.
Correct Answer: B — Holes
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Q. What is the mass defect in a nucleus?
A.
The difference between the mass of the nucleus and the sum of the masses of its nucleons
B.
The mass of the nucleus itself
C.
The mass of the electrons surrounding the nucleus
D.
The mass of the binding energy
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Solution
The mass defect is the difference between the mass of the nucleus and the sum of the masses of its individual nucleons.
Correct Answer: A — The difference between the mass of the nucleus and the sum of the masses of its nucleons
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Q. What is the maximum kinetic energy of photoelectrons emitted if the incident light has a frequency of 8 x 10^14 Hz and the work function is 3 eV?
A.
1 eV
B.
3 eV
C.
5 eV
D.
7 eV
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Solution
Maximum kinetic energy (K.E.) = hf - Φ = (6.626 x 10^-34 J·s)(8 x 10^14 Hz) - 3 eV = 5 eV.
Correct Answer: C — 5 eV
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Q. What is the maximum kinetic energy of photoelectrons emitted when light of frequency 8 x 10^14 Hz is incident on a metal with work function 3 eV?
A.
1 eV
B.
3 eV
C.
5 eV
D.
7 eV
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Solution
Maximum kinetic energy (K.E.) = hν - Φ = (4.14 x 10^-15 eV·s)(8 x 10^14 Hz) - 3 eV = 5 eV.
Correct Answer: C — 5 eV
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Q. What is the maximum kinetic energy of photoelectrons if the incident light has a frequency of 8 x 10^14 Hz and the work function is 3 eV?
A.
1 eV
B.
3 eV
C.
5 eV
D.
7 eV
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Solution
Maximum kinetic energy (K.E.) = hν - Φ = (4.14 x 10^-15 eV·s)(8 x 10^14 Hz) - 3 eV = 5 eV.
Correct Answer: C — 5 eV
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Q. What is the maximum number of electrons in the d-subshell?
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Solution
The d-subshell can hold a maximum of 10 electrons.
Correct Answer: C — 10
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Q. What is the maximum number of electrons that can occupy a single p subshell?
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Solution
A p subshell can hold a maximum of 6 electrons, as it has three orbitals each capable of holding 2 electrons.
Correct Answer: B — 6
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Q. What is the maximum number of electrons that can occupy the d subshell?
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Solution
The d subshell can hold a maximum of 10 electrons.
Correct Answer: C — 10
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Q. What is the maximum number of electrons that can occupy the f subshell?
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Solution
The f subshell can hold a maximum of 14 electrons (7 orbitals, each can hold 2).
Correct Answer: D — 14
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Q. What is the maximum number of electrons that can occupy the n=3 energy level?
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Solution
The maximum number of electrons in an energy level is given by the formula 2n^2. For n=3, it is 2(3^2) = 18.
Correct Answer: C — 18
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Q. What is the maximum wavelength of light that can cause the photoelectric effect in a metal with a work function of 2.0 eV?
A.
620 nm
B.
400 nm
C.
500 nm
D.
300 nm
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Solution
The maximum wavelength λ_max can be calculated using λ_max = hc/E, where E = 2.0 eV = 3.2 x 10^-19 J. Thus, λ_max = (6.63 x 10^-34 * 3 x 10^8) / (3.2 x 10^-19) = 620 nm.
Correct Answer: A — 620 nm
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