Modern Physics
Q. What is the work function of a metal if the threshold frequency is 5 x 10^14 Hz?
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A.
3.1 eV
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B.
2.5 eV
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C.
4.1 eV
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D.
1.6 eV
Solution
The work function φ can be calculated using φ = hf, where h = 6.63 x 10^-34 J.s and f = 5 x 10^14 Hz, giving φ ≈ 3.1 eV.
Correct Answer: A — 3.1 eV
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Q. What is the work function of a metal?
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A.
The energy required to ionize an atom
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B.
The energy required to remove an electron from the surface of a metal
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C.
The energy of the emitted electrons
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D.
The energy of the incident photons
Solution
The work function is the minimum energy required to remove an electron from the surface of a metal.
Correct Answer: B — The energy required to remove an electron from the surface of a metal
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Q. What type of decay involves the emission of a helium nucleus?
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A.
Alpha decay
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B.
Beta decay
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C.
Gamma decay
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D.
Neutron decay
Solution
Alpha decay involves the emission of an alpha particle, which is a helium nucleus.
Correct Answer: A — Alpha decay
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Q. What type of radiation is emitted during alpha decay?
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A.
Electrons
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B.
Helium nuclei
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C.
Gamma rays
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D.
Neutrons
Solution
During alpha decay, helium nuclei (alpha particles) are emitted from the nucleus.
Correct Answer: B — Helium nuclei
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Q. What type of radiation is emitted during beta decay?
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A.
Alpha particles
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B.
Beta particles
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C.
Gamma rays
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D.
Neutrons
Solution
Beta decay involves the emission of beta particles, which are electrons or positrons.
Correct Answer: B — Beta particles
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Q. What type of radiation is most penetrating?
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A.
Alpha radiation
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B.
Beta radiation
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C.
Gamma radiation
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D.
Neutron radiation
Solution
Gamma radiation is the most penetrating type of radiation.
Correct Answer: C — Gamma radiation
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Q. What type of semiconductor behavior is exhibited by a material with a very small band gap?
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A.
Insulator
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B.
Conductor
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C.
Superconductor
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D.
Semiconductor
Solution
A material with a very small band gap behaves like a semiconductor, allowing some charge carriers to be thermally excited.
Correct Answer: D — Semiconductor
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Q. What type of semiconductor is formed when silicon is doped with phosphorus?
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A.
p-type
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B.
n-type
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C.
Intrinsic
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D.
Superconductor
Solution
Doping silicon with phosphorus creates an n-type semiconductor due to the extra electrons contributed by phosphorus.
Correct Answer: B — n-type
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Q. Which device utilizes the p-n junction principle?
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A.
Resistor
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B.
Capacitor
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C.
Diode
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D.
Inductor
Solution
A diode is a semiconductor device that utilizes the p-n junction principle to allow current to flow in one direction.
Correct Answer: C — Diode
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Q. Which gate can be used to create a NOT operation using only NAND gates?
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A.
Two NAND gates
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B.
One NAND gate
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C.
Three NAND gates
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D.
Four NAND gates
Solution
A NOT operation can be created using two NAND gates.
Correct Answer: A — Two NAND gates
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Q. Which gate can be used to invert the output of an AND gate?
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A.
OR Gate
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B.
NAND Gate
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C.
XOR Gate
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D.
NOT Gate
Solution
A NAND gate inverts the output of an AND gate.
Correct Answer: B — NAND Gate
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Q. Which gate outputs true only when all inputs are false?
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A.
AND
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B.
OR
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C.
NOR
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D.
NAND
Solution
The NOR gate outputs true only when all inputs are false.
Correct Answer: C — NOR
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Q. Which isotope is commonly used in nuclear reactors?
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A.
Uranium-238
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B.
Carbon-14
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C.
Hydrogen-1
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D.
Oxygen-16
Solution
Uranium-238 is commonly used as fuel in nuclear reactors.
Correct Answer: A — Uranium-238
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Q. Which logic gate is equivalent to an AND gate followed by a NOT gate?
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A.
OR
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B.
NAND
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C.
NOR
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D.
XOR
Solution
The NAND gate is equivalent to an AND gate followed by a NOT gate, as it inverts the output of the AND gate.
Correct Answer: B — NAND
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Q. Which logic gate is represented by the symbol '⊕'?
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A.
AND Gate
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B.
OR Gate
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C.
NAND Gate
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D.
XOR Gate
Solution
The symbol '⊕' represents the XOR gate.
Correct Answer: D — XOR Gate
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Q. Which logic gate outputs true only when all inputs are false?
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A.
AND
-
B.
OR
-
C.
NOR
-
D.
NAND
Solution
The NOR gate outputs true (1) only when all inputs are false (0).
Correct Answer: C — NOR
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Q. Which logic gate outputs true only when all inputs are true?
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A.
AND
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B.
OR
-
C.
NOT
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D.
NAND
Solution
The AND gate outputs true only when all its inputs are true.
Correct Answer: A — AND
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Q. Which logic gate outputs true only when all its inputs are true?
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A.
AND Gate
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B.
OR Gate
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C.
NOT Gate
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D.
NAND Gate
Solution
The AND gate outputs true only when all its inputs are true.
Correct Answer: A — AND Gate
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Q. Which logic gate outputs true only when both inputs are false?
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A.
AND
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B.
OR
-
C.
NAND
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D.
NOR
Solution
The NOR gate outputs true only when both inputs are false.
Correct Answer: D — NOR
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Q. Which modulation technique is most commonly used in digital communication systems?
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A.
Amplitude Modulation (AM)
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B.
Frequency Modulation (FM)
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C.
Phase Shift Keying (PSK)
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D.
Quadrature Amplitude Modulation (QAM)
Solution
Quadrature Amplitude Modulation (QAM) is widely used in digital communication systems due to its efficiency in transmitting data.
Correct Answer: D — Quadrature Amplitude Modulation (QAM)
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Q. Which modulation technique is most commonly used in FM radio broadcasting?
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A.
Amplitude Modulation
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B.
Frequency Modulation
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C.
Phase Modulation
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D.
Pulse Code Modulation
Solution
Frequency Modulation (FM) is the standard technique used in FM radio broadcasting due to its resistance to noise.
Correct Answer: B — Frequency Modulation
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Q. Which modulation technique is most commonly used in television broadcasting?
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A.
Amplitude Modulation (AM)
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B.
Frequency Modulation (FM)
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C.
Phase Modulation (PM)
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D.
Pulse Code Modulation (PCM)
Solution
Frequency Modulation (FM) is commonly used in television broadcasting due to its better noise immunity.
Correct Answer: B — Frequency Modulation (FM)
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Q. Which modulation technique is used to transmit digital data over an analog channel?
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A.
AM
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B.
FM
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C.
PSK
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D.
ASK
Solution
Phase Shift Keying (PSK) is a modulation technique used to transmit digital data over an analog channel.
Correct Answer: C — PSK
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Q. Which modulation technique varies the amplitude of the carrier signal?
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A.
Frequency Modulation
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B.
Amplitude Modulation
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C.
Phase Modulation
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D.
Pulse Modulation
Solution
Amplitude Modulation (AM) varies the amplitude of the carrier signal.
Correct Answer: B — Amplitude Modulation
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Q. Which of the following describes the behavior of a Zener diode?
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A.
Acts as a regular diode
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B.
Allows current to flow in both directions
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C.
Maintains a constant voltage
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D.
Has no breakdown voltage
Solution
A Zener diode is designed to maintain a constant voltage across it when reverse-biased, allowing it to regulate voltage.
Correct Answer: C — Maintains a constant voltage
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Q. Which of the following devices is based on the principle of semiconductors?
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A.
Transformer
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B.
Capacitor
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C.
Transistor
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D.
Inductor
Solution
A transistor is a semiconductor device that can amplify or switch electronic signals and electrical power.
Correct Answer: C — Transistor
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Q. Which of the following gates is a universal gate?
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A.
AND
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B.
OR
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C.
NAND
-
D.
XOR
Solution
The NAND gate is a universal gate because it can be used to create any other gate.
Correct Answer: C — NAND
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Q. Which of the following gates is considered a universal gate?
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A.
AND Gate
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B.
OR Gate
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C.
NAND Gate
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D.
XOR Gate
Solution
The NAND gate is considered a universal gate because it can be used to create any other gate.
Correct Answer: C — NAND Gate
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Q. Which of the following gates is equivalent to an AND gate followed by a NOT gate?
-
A.
OR
-
B.
NAND
-
C.
NOR
-
D.
XOR
Solution
The output of an AND gate followed by a NOT gate is a NAND gate.
Correct Answer: B — NAND
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Q. Which of the following is a characteristic of alpha particles?
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A.
High penetration power
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B.
No charge
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C.
Consist of 2 protons and 2 neutrons
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D.
Lightest form of radiation
Solution
Alpha particles consist of 2 protons and 2 neutrons, making them a helium nucleus.
Correct Answer: C — Consist of 2 protons and 2 neutrons
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