Modern Physics
Q. In a diode, what is the region called where no charge carriers are present?
A.
Conduction band
B.
Valence band
C.
Depletion region
D.
N-type region
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Solution
The depletion region in a diode is the area where no charge carriers are present.
Correct Answer: C — Depletion region
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Q. In a diode, what is the region called where no current flows?
A.
Forward bias
B.
Reverse bias
C.
Depletion region
D.
Conduction region
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Solution
The depletion region is the area in a diode where no current flows under reverse bias.
Correct Answer: C — Depletion region
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Q. In a hydrogen atom, the energy levels are quantized. What is the formula for the energy of the nth level?
A.
E_n = -13.6/n^2 eV
B.
E_n = -13.6n^2 eV
C.
E_n = -13.6/n eV
D.
E_n = -13.6n eV
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Solution
The energy levels of a hydrogen atom are given by E_n = -13.6/n^2 eV, where n is the principal quantum number.
Correct Answer: A — E_n = -13.6/n^2 eV
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Q. In a hydrogen atom, what is the energy of the electron in the ground state?
A.
-13.6 eV
B.
-3.4 eV
C.
-1.51 eV
D.
0 eV
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Solution
The energy of the electron in the ground state of a hydrogen atom is -13.6 eV.
Correct Answer: A — -13.6 eV
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Q. In a hydrogen atom, what is the energy of the electron in the n=2 state?
A.
-3.4 eV
B.
-13.6 eV
C.
-1.51 eV
D.
-0.85 eV
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Solution
The energy of an electron in a hydrogen atom in the n=2 state is given by E_n = -13.6/n^2 = -13.6/4 = -3.4 eV.
Correct Answer: A — -3.4 eV
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Q. In a hydrogen atom, what is the wavelength of the emitted photon when an electron transitions from n=3 to n=2?
A.
656 nm
B.
486 nm
C.
434 nm
D.
410 nm
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Solution
Using the Rydberg formula, the wavelength for the transition from n=3 to n=2 is approximately 486 nm.
Correct Answer: B — 486 nm
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Q. In a hydrogen atom, which transition emits the photon with the highest energy?
A.
n=2 to n=1
B.
n=3 to n=2
C.
n=4 to n=3
D.
n=5 to n=4
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Solution
The energy of the emitted photon is highest for the transition from n=2 to n=1, as it involves the largest energy difference.
Correct Answer: A — n=2 to n=1
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Q. In a hydrogen atom, which transition would emit the highest energy photon?
A.
n=2 to n=1
B.
n=3 to n=2
C.
n=4 to n=3
D.
n=5 to n=4
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Solution
The energy of the photon emitted is highest for the transition from n=2 to n=1, as it involves the largest energy difference.
Correct Answer: A — n=2 to n=1
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Q. In a hydrogen atom, which transition would emit the photon with the highest energy?
A.
n=2 to n=1
B.
n=3 to n=2
C.
n=4 to n=3
D.
n=5 to n=4
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Solution
The energy of the emitted photon is highest for the transition from n=2 to n=1, as it involves the largest energy difference.
Correct Answer: A — n=2 to n=1
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Q. In a nuclear reaction, what is conserved?
A.
Mass only
B.
Charge only
C.
Mass and charge
D.
Energy only
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Solution
In nuclear reactions, both mass and charge are conserved, according to the law of conservation of mass-energy and charge.
Correct Answer: C — Mass and charge
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Q. In a nuclear reaction, what is the term for the energy released when a nucleus is formed from its constituent nucleons?
A.
Binding energy
B.
Kinetic energy
C.
Potential energy
D.
Thermal energy
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Solution
The energy released when a nucleus is formed from its constituent nucleons is called binding energy.
Correct Answer: A — Binding energy
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Q. In a nuclear reaction, what is the term for the energy released?
A.
Kinetic energy
B.
Potential energy
C.
Binding energy
D.
Nuclear energy
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Solution
The energy released in a nuclear reaction is referred to as nuclear energy, which is a result of changes in the binding energy of the nucleus.
Correct Answer: D — Nuclear energy
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Q. In a nuclear reaction, what is the term for the mass difference between the reactants and products?
A.
Mass defect
B.
Binding energy
C.
Nuclear fusion
D.
Nuclear fission
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Solution
The mass defect is the difference in mass between the reactants and products in a nuclear reaction, which is related to the binding energy.
Correct Answer: A — Mass defect
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Q. In a p-n junction diode, what happens when it is forward biased?
A.
Depletion region widens
B.
Current flows easily
C.
No current flows
D.
Reverse breakdown occurs
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Solution
When a p-n junction diode is forward biased, the depletion region narrows, allowing current to flow easily through the junction.
Correct Answer: B — Current flows easily
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Q. In a p-n junction diode, what happens when it is reverse-biased?
A.
Current flows freely
B.
Depletion region widens
C.
Holes move towards the n-side
D.
Electrons move towards the p-side
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Solution
When a p-n junction diode is reverse-biased, the depletion region widens, preventing current flow.
Correct Answer: B — Depletion region widens
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Q. In a p-n junction, what is formed at the junction region?
A.
Electric field
B.
Magnetic field
C.
Thermal field
D.
Gravitational field
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Solution
An electric field is formed at the p-n junction due to the diffusion of charge carriers.
Correct Answer: A — Electric field
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Q. In a p-n junction, what is the region called where no charge carriers are present?
A.
Depletion region
B.
Conduction band
C.
Valence band
D.
Neutral zone
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Solution
The depletion region is the area around the p-n junction where charge carriers are depleted, creating an electric field.
Correct Answer: A — Depletion region
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Q. In a p-n junction, what is the region called where no charge carriers exist?
A.
Depletion region
B.
Conduction band
C.
Valence band
D.
Neutral zone
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Solution
The depletion region is the area around the p-n junction where charge carriers have recombined, leaving behind immobile ions.
Correct Answer: A — Depletion region
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Q. In a photoelectric experiment, if the frequency of light is just above the threshold frequency, what can be said about the emitted electrons?
A.
They have maximum kinetic energy
B.
They are emitted with zero kinetic energy
C.
They are emitted with high kinetic energy
D.
No electrons are emitted
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Solution
If the frequency of light is just above the threshold frequency, the emitted electrons will have zero kinetic energy, as all the energy is used to overcome the work function.
Correct Answer: B — They are emitted with zero kinetic energy
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Q. In a photoelectric experiment, if the stopping potential is increased, what does it indicate about the emitted electrons?
A.
They have higher kinetic energy
B.
They have lower kinetic energy
C.
They are emitted at a lower rate
D.
They are not emitted
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Solution
Increasing the stopping potential indicates that the emitted electrons have higher kinetic energy, as more energy is required to stop them.
Correct Answer: A — They have higher kinetic energy
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Q. In a photoelectric experiment, if the stopping potential is increased, what happens to the current?
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
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Solution
Increasing the stopping potential reduces the number of electrons reaching the anode, thus decreasing the current.
Correct Answer: B — It decreases
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Q. In a photoelectric experiment, if the stopping potential is increased, what happens to the energy of the emitted electrons?
A.
It increases
B.
It decreases
C.
It remains the same
D.
It becomes negative
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Solution
The stopping potential does not affect the energy of the emitted electrons; it only affects the number of electrons reaching the detector.
Correct Answer: C — It remains the same
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Q. In a photoelectric experiment, if the stopping potential is increased, what happens to the maximum kinetic energy of the emitted electrons?
A.
It increases
B.
It decreases
C.
It remains the same
D.
It becomes zero
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Solution
Increasing the stopping potential increases the maximum kinetic energy of the emitted electrons, as the stopping potential is directly related to the kinetic energy of the electrons.
Correct Answer: A — It increases
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Q. In a semiconductor, what is the term for the energy required to move an electron from the valence band to the conduction band?
A.
Ionization energy
B.
Band gap energy
C.
Thermal energy
D.
Activation energy
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Solution
The energy required to move an electron from the valence band to the conduction band is known as the band gap energy.
Correct Answer: B — Band gap energy
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Q. In amplitude modulation (AM), what does the amplitude of the carrier wave represent?
A.
The frequency of the modulating signal
B.
The phase of the modulating signal
C.
The information signal
D.
The power of the carrier wave
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Solution
In AM, the amplitude of the carrier wave varies in accordance with the amplitude of the modulating signal, which carries the information.
Correct Answer: C — The information signal
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Q. In amplitude modulation (AM), what does the carrier wave represent?
A.
The information signal
B.
The frequency of the modulated signal
C.
The average power of the signal
D.
The high-frequency signal that carries the information
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Solution
In AM, the carrier wave is a high-frequency signal that carries the information signal by varying its amplitude.
Correct Answer: D — The high-frequency signal that carries the information
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Q. In beta decay, which particle is emitted from the nucleus?
A.
Alpha particle
B.
Beta particle
C.
Gamma ray
D.
Neutron
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Solution
In beta decay, a beta particle (which is an electron or positron) is emitted from the nucleus.
Correct Answer: B — Beta particle
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Q. In digital communication, what does the term 'bit rate' refer to?
A.
The number of bits transmitted per second
B.
The number of bits stored in a device
C.
The number of bits in a signal
D.
The number of bits required for modulation
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Solution
Bit rate is defined as the number of bits transmitted per second in a digital communication system.
Correct Answer: A — The number of bits transmitted per second
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Q. In nuclear fission, what is released apart from energy?
A.
Neutrons
B.
Protons
C.
Electrons
D.
Photons
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Solution
Nuclear fission releases neutrons along with a significant amount of energy.
Correct Answer: A — Neutrons
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Q. In nuclear fission, what is the primary product of the reaction?
A.
Helium
B.
Neutrons
C.
Protons
D.
Alpha particles
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Solution
In nuclear fission, the primary products are neutrons, which can further induce fission in nearby nuclei.
Correct Answer: B — Neutrons
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