Q. If the wavelength of light is halved, what happens to its frequency? (2021)
A.
It is halved
B.
It remains the same
C.
It is doubled
D.
It is quadrupled
Show solution
Solution
Frequency (f) is inversely proportional to wavelength (λ). If λ is halved, f is doubled.
Correct Answer:
C
— It is doubled
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Q. If the wavelength of light is halved, what happens to the energy of the photons? (2020)
A.
It is halved
B.
It is doubled
C.
It remains the same
D.
It is quadrupled
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Solution
Energy is inversely proportional to wavelength. Halving the wavelength doubles the energy.
Correct Answer:
B
— It is doubled
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Q. In a nuclear reaction, if a nucleus emits an alpha particle, what happens to its atomic number? (2023)
A.
It increases by 2
B.
It decreases by 2
C.
It remains the same
D.
It decreases by 4
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Solution
An alpha particle consists of 2 protons and 2 neutrons, so the atomic number decreases by 2.
Correct Answer:
B
— It decreases by 2
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Q. In the photoelectric effect, if the frequency of incident light is doubled, what happens to the kinetic energy of emitted electrons? (2020)
A.
It doubles
B.
It quadruples
C.
It remains the same
D.
It becomes zero
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Solution
Kinetic energy (KE) = hf - φ. If frequency is doubled, KE increases by a factor of 4.
Correct Answer:
B
— It quadruples
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Q. What is the de Broglie wavelength of an electron moving with a velocity of 1 x 10^6 m/s? (mass of electron = 9.11 x 10^-31 kg) (2022)
A.
6.63 x 10^-24 m
B.
6.63 x 10^-22 m
C.
6.63 x 10^-20 m
D.
6.63 x 10^-18 m
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Solution
λ = h / p = h / (mv) = 6.63 x 10^-34 / (9.11 x 10^-31 * 1 x 10^6) = 6.63 x 10^-24 m.
Correct Answer:
A
— 6.63 x 10^-24 m
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Q. What is the energy of a photon emitted when an electron transitions from n=3 to n=2 in a hydrogen atom? (Rydberg constant R = 1.097 x 10^7 m^-1) (2021)
A.
1.89 eV
B.
3.40 eV
C.
4.86 eV
D.
5.13 eV
Show solution
Solution
Energy = 13.6 eV * (1/n1^2 - 1/n2^2) = 13.6 * (1/2^2 - 1/3^2) = 3.40 eV.
Correct Answer:
B
— 3.40 eV
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Q. What is the main component of a nuclear reactor that slows down neutrons? (2023)
A.
Control rods
B.
Moderator
C.
Coolant
D.
Shielding
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Solution
The moderator is the main component in a nuclear reactor that slows down neutrons to sustain the nuclear chain reaction.
Correct Answer:
B
— Moderator
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Q. What is the mass-energy equivalence formula proposed by Einstein? (2019)
A.
E = mc^2
B.
E = mv^2
C.
E = mgh
D.
E = hf
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Solution
The mass-energy equivalence formula is E = mc^2, which states that energy (E) is equal to mass (m) times the speed of light (c) squared.
Correct Answer:
A
— E = mc^2
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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 4.0 eV? (2023)
A.
310 nm
B.
620 nm
C.
1240 nm
D.
1550 nm
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Solution
Maximum wavelength (λ) = hc/φ. λ = (1240 eV.nm) / 4.0 eV = 310 nm.
Correct Answer:
A
— 310 nm
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Q. What is the minimum energy required to remove an electron from a metal surface with a work function of 2.5 eV? (2022)
A.
1.5 eV
B.
2.5 eV
C.
3.5 eV
D.
4.5 eV
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Solution
The minimum energy required to remove an electron is equal to the work function of the metal, which is 2.5 eV.
Correct Answer:
B
— 2.5 eV
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Q. What is the minimum energy required to remove an electron from a metal surface with a work function of 2 eV? (2021)
A.
1 eV
B.
2 eV
C.
3 eV
D.
4 eV
Show solution
Solution
The minimum energy required is equal to the work function, which is 2 eV.
Correct Answer:
B
— 2 eV
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Q. What is the minimum energy required to remove an electron from the surface of a metal with a work function of 2.5 eV? (2023)
A.
1.5 eV
B.
2.5 eV
C.
3.5 eV
D.
4.5 eV
Show solution
Solution
The minimum energy required to remove an electron is equal to the work function of the metal, which is 2.5 eV.
Correct Answer:
B
— 2.5 eV
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Q. What is the principal quantum number of an electron in the ground state of a hydrogen atom? (2022)
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Solution
The ground state of hydrogen corresponds to n = 1.
Correct Answer:
B
— 1
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Q. What is the principal quantum number of an electron in the third energy level? (2023)
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Solution
The principal quantum number (n) indicates the energy level. For the third energy level, n = 3.
Correct Answer:
C
— 3
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Q. What is the significance of the Rydberg constant? (2022)
A.
It determines the energy levels of an atom
B.
It is used to calculate the wavelengths of spectral lines
C.
It is a measure of atomic mass
D.
It relates to the speed of light
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Solution
The Rydberg constant is used to calculate the wavelengths of spectral lines in hydrogen and other hydrogen-like atoms.
Correct Answer:
B
— It is used to calculate the wavelengths of spectral lines
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Q. What is the significance of the wave function in quantum mechanics? (2023)
A.
It describes the position of a particle
B.
It gives the probability of finding a particle
C.
It determines the mass of a particle
D.
It is irrelevant
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Solution
The wave function provides the probability distribution of a particle's position.
Correct Answer:
B
— It gives the probability of finding a particle
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Q. Which of the following statements is true about the nucleus of an atom? (2019)
A.
It contains only protons
B.
It contains only neutrons
C.
It contains protons and neutrons
D.
It contains electrons
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Solution
The nucleus of an atom contains protons and neutrons, which are collectively known as nucleons.
Correct Answer:
C
— It contains protons and neutrons
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Q. Which of the following statements is true regarding the uncertainty principle? (2023)
A.
It applies only to macroscopic objects
B.
It states that position and momentum cannot be known simultaneously
C.
It is only applicable in classical mechanics
D.
It has no practical implications
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Solution
The uncertainty principle states that position and momentum cannot be precisely known at the same time.
Correct Answer:
B
— It states that position and momentum cannot be known simultaneously
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