Modern Physics
Q. What is the primary force that holds the protons and neutrons together in the nucleus?
A.
Electromagnetic force
B.
Gravitational force
C.
Strong nuclear force
D.
Weak nuclear force
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Solution
The strong nuclear force is the primary force that holds protons and neutrons together in the nucleus, overcoming the electromagnetic repulsion between protons.
Correct Answer: C — Strong nuclear force
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Q. What is the primary function of a diode in a circuit?
A.
Amplification
B.
Rectification
C.
Capacitance
D.
Inductance
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Solution
The primary function of a diode is rectification, allowing current to flow in one direction only.
Correct Answer: B — Rectification
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Q. What is the primary function of a modulator in a communication system?
A.
To amplify the signal
B.
To convert the signal into a suitable form for transmission
C.
To demodulate the received signal
D.
To filter out noise
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Solution
A modulator converts the baseband signal into a form suitable for transmission over a communication channel.
Correct Answer: B — To convert the signal into a suitable form for transmission
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Q. What is the primary function of a transistor in semiconductor technology?
A.
Switching
B.
Storage
C.
Transmission
D.
Resistance
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Solution
The primary function of a transistor is switching, allowing it to control electrical signals.
Correct Answer: A — Switching
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Q. What is the primary function of a transistor?
A.
Rectification
B.
Amplification
C.
Capacitance
D.
Inductance
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Solution
The primary function of a transistor is amplification of electrical signals.
Correct Answer: B — Amplification
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Q. What is the primary function of a transponder in satellite communication?
A.
To amplify the signal
B.
To receive and retransmit signals
C.
To modulate the signal
D.
To filter out noise
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Solution
A transponder in satellite communication receives signals from the ground, processes them, and retransmits them back to Earth.
Correct Answer: B — To receive and retransmit signals
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Q. What is the primary function of an antenna in a communication system?
A.
To amplify the signal
B.
To convert electrical signals into electromagnetic waves
C.
To modulate the signal
D.
To demodulate the signal
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Solution
An antenna converts electrical signals into electromagnetic waves for transmission and vice versa for reception.
Correct Answer: B — To convert electrical signals into electromagnetic waves
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Q. What is the primary mechanism of current flow in semiconductors?
A.
Electron flow only
B.
Hole flow only
C.
Both electron and hole flow
D.
Ionic flow
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Solution
Current flow in semiconductors occurs due to the movement of both electrons and holes.
Correct Answer: C — Both electron and hole flow
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Q. What is the primary product of a nuclear fusion reaction in stars?
A.
Helium
B.
Hydrogen
C.
Carbon
D.
Uranium
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Solution
The primary product of nuclear fusion reactions in stars is helium, formed from the fusion of hydrogen nuclei.
Correct Answer: A — Helium
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Q. What is the primary product of nuclear fusion in stars like the Sun?
A.
Helium
B.
Hydrogen
C.
Carbon
D.
Oxygen
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Solution
The primary product of nuclear fusion in stars like the Sun is helium, formed from the fusion of hydrogen nuclei.
Correct Answer: A — Helium
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Q. What is the primary purpose of a demodulator in a communication system?
A.
To amplify the signal
B.
To convert the signal back to its original form
C.
To filter the noise
D.
To encode the signal
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Solution
A demodulator converts the modulated signal back to its original form.
Correct Answer: B — To convert the signal back to its original form
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Q. What is the primary purpose of a modulator in a communication system?
A.
To amplify the signal
B.
To convert digital signals to analog
C.
To filter noise
D.
To encode information
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Solution
A modulator converts digital signals to analog for transmission.
Correct Answer: B — To convert digital signals to analog
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Q. What is the primary purpose of modulation in communication systems?
A.
To increase the bandwidth of the signal
B.
To reduce noise in the signal
C.
To allow the transmission of signals over long distances
D.
To convert digital signals to analog signals
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Solution
Modulation allows signals to be transmitted over long distances by shifting the frequency of the signal to a higher range, making it suitable for transmission through various media.
Correct Answer: C — To allow the transmission of signals over long distances
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Q. What is the primary type of decay for an unstable nucleus with too many protons?
A.
Alpha decay
B.
Beta decay
C.
Gamma decay
D.
Positron emission
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Solution
An unstable nucleus with too many protons typically undergoes alpha decay, where it emits an alpha particle (2 protons and 2 neutrons) to become more stable.
Correct Answer: A — Alpha decay
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Q. What is the primary type of radiation emitted by uranium-238?
A.
Alpha radiation
B.
Beta radiation
C.
Gamma radiation
D.
X-rays
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Solution
Uranium-238 primarily emits alpha radiation during its decay process.
Correct Answer: A — Alpha radiation
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Q. What is the primary type of radiation emitted during alpha decay?
A.
Helium nucleus
B.
Electron
C.
Photon
D.
Neutrino
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Solution
During alpha decay, an alpha particle, which is a helium nucleus (2 protons and 2 neutrons), is emitted.
Correct Answer: A — Helium nucleus
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Q. What is the primary use of nuclear fission in power plants?
A.
To produce nuclear weapons
B.
To generate heat for electricity
C.
To create isotopes for medical use
D.
To study nuclear reactions
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Solution
Nuclear fission is primarily used in power plants to generate heat, which is then converted into electricity.
Correct Answer: B — To generate heat for electricity
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Q. What is the primary use of nuclear fission?
A.
Medical imaging
B.
Nuclear power generation
C.
Smoke detectors
D.
Radiocarbon dating
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Solution
Nuclear fission is primarily used for nuclear power generation.
Correct Answer: B — Nuclear power generation
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Q. What is the primary use of nuclear reactors?
A.
To produce nuclear weapons
B.
To generate electricity
C.
To create isotopes for medical use
D.
To study nuclear physics
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Solution
The primary use of nuclear reactors is to generate electricity through controlled nuclear fission.
Correct Answer: B — To generate electricity
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Q. What is the primary use of radioactive isotopes in medicine?
A.
Energy production
B.
Diagnostic imaging
C.
Food preservation
D.
Industrial applications
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Solution
Radioactive isotopes are primarily used in medicine for diagnostic imaging and treatment.
Correct Answer: B — Diagnostic imaging
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Q. What is the principal quantum number for an electron in the 4th shell?
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Solution
The principal quantum number (n) corresponds to the shell number. For the 4th shell, n=4.
Correct Answer: D — 4
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Q. What is the principal quantum number of an electron in the 3p orbital?
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Solution
The principal quantum number (n) indicates the energy level of an electron. For a 3p orbital, n = 3.
Correct Answer: C — 3
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Q. What is the principal quantum number of an electron in the 4s orbital?
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Solution
The principal quantum number (n) indicates the energy level of an electron. For the 4s orbital, n = 4.
Correct Answer: C — 4
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Q. What is the principle behind nuclear fission?
A.
Splitting of heavy nuclei
B.
Combining of light nuclei
C.
Emission of photons
D.
Absorption of neutrons
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Solution
Nuclear fission is the process where a heavy nucleus splits into two or more lighter nuclei, releasing energy.
Correct Answer: A — Splitting of heavy nuclei
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Q. What is the principle behind the operation of a laser?
A.
Spontaneous emission
B.
Stimulated emission
C.
Absorption
D.
Reflection
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Solution
Lasers operate on the principle of stimulated emission, where an incoming photon stimulates an excited electron to emit a photon of the same energy, phase, and direction.
Correct Answer: B — Stimulated emission
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Q. What is the process called when a heavy nucleus splits into two lighter nuclei?
A.
Nuclear fusion
B.
Nuclear fission
C.
Radioactive decay
D.
Nuclear transmutation
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Solution
Nuclear fission is the process in which a heavy nucleus splits into two lighter nuclei, releasing energy in the process.
Correct Answer: B — Nuclear fission
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Q. What is the purpose of a demodulator in a communication system?
A.
To encode the signal for transmission
B.
To convert the modulated signal back to its original form
C.
To amplify the received signal
D.
To filter out unwanted frequencies
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Solution
A demodulator's purpose is to convert the modulated signal back to its original baseband form for further processing.
Correct Answer: B — To convert the modulated signal back to its original form
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Q. What is the relationship between the frequency of incident light and the number of emitted electrons in the photoelectric effect?
A.
Directly proportional
B.
Inversely proportional
C.
No relationship
D.
Exponential relationship
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Solution
The number of emitted electrons is related to the intensity of light, not the frequency, as long as the frequency is above the threshold.
Correct Answer: C — No relationship
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Q. What is the relationship between the intensity of light and the energy of individual photons in the photoelectric effect?
A.
Directly proportional
B.
Inversely proportional
C.
Independent
D.
Depends on frequency
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Solution
The energy of individual photons is dependent on frequency (E = hν) and not on intensity.
Correct Answer: C — Independent
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Q. What is the relationship between the number of emitted electrons and the intensity of light in the photoelectric effect?
A.
Directly proportional
B.
Inversely proportional
C.
No relationship
D.
Exponential relationship
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Solution
The number of emitted electrons is directly proportional to the intensity of light, provided the frequency is above the threshold frequency.
Correct Answer: A — Directly proportional
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