Q. If A = 0 and B = 1, what is the output of the XOR gate?
A.0
B.1
C.2
D.Undefined
Solution
The XOR gate outputs 1 when the inputs are different. Since A is 0 and B is 1, the output is 1.
Correct Answer: B — 1
Q. If A = 1 and B = 1, what is the output of the AND gate?
A.0
B.1
C.2
D.Undefined
Solution
The AND gate outputs 1 only when both inputs are high. Since A = 1 and B = 1, the output is 1.
Correct Answer: B — 1
Q. If A = 1, B = 1, and C = 0, what is the output of A OR (B AND C)?
A.0
B.1
C.2
D.Undefined
Solution
B AND C = 1 AND 0 = 0. Then, A OR 0 = 1 OR 0 = 1.
Correct Answer: B — 1
Q. If A = 1, B = 1, and C = 0, what is the output of the expression (A OR B) AND C?
A.0
B.1
C.2
D.3
Solution
First, evaluate A OR B, which is 1 OR 1 = 1. Then, 1 AND 0 = 0.
Correct Answer: A — 0
Q. If a metal has a work function of 2 eV, what is the minimum wavelength of light required to cause the photoelectric effect?
A.620 nm
B.310 nm
C.1240 nm
D.500 nm
Solution
Using the equation λ = hc/E, where E = 2 eV = 2 * 1.6 x 10^-19 J, we find the minimum wavelength λ = (6.63 x 10^-34 J·s * 3 x 10^8 m/s) / (2 * 1.6 x 10^-19 J) = 310 nm.
Correct Answer: B — 310 nm
Q. If a metal has a work function of 2 eV, what is the threshold wavelength for the photoelectric effect?
A.620 nm
B.400 nm
C.500 nm
D.300 nm
Solution
The threshold wavelength can be calculated using the equation λ = hc/W. Substituting h = 4.14 x 10^-15 eV·s, c = 3 x 10^8 m/s, and W = 2 eV gives λ = 620 nm.
Correct Answer: A — 620 nm
Q. If a metal has a work function of 2.0 eV, what is the maximum kinetic energy of the emitted electrons when illuminated with light of 5.0 eV energy?
A.3.0 eV
B.2.0 eV
C.5.0 eV
D.0 eV
Solution
The maximum kinetic energy can be calculated using KE = hf - φ. Here, KE = 5.0 eV - 2.0 eV = 3.0 eV.
Correct Answer: A — 3.0 eV
Q. If a metal has a work function of 4 eV, what is the threshold frequency for the photoelectric effect?
A.1.5 x 10^14 Hz
B.3.2 x 10^14 Hz
C.5.0 x 10^14 Hz
D.6.3 x 10^14 Hz
Solution
The threshold frequency can be calculated using the formula f = φ/h, where h is Planck's constant (4.14 x 10^-15 eV·s).
Correct Answer: B — 3.2 x 10^14 Hz
Q. If the frequency of incident light is doubled, what happens to the kinetic energy of the emitted electrons?
A.It remains the same
B.It doubles
C.It quadruples
D.It decreases
Solution
The kinetic energy of the emitted electrons is given by KE = hf - φ. If the frequency is doubled, the kinetic energy increases as it is directly proportional to frequency.
Correct Answer: B — It doubles
Q. If the intensity of light is doubled while keeping the frequency constant, what happens to the number of emitted electrons?
A.It doubles
B.It remains the same
C.It is halved
D.It becomes zero
Solution
Doubling the intensity of light increases the number of photons incident on the surface, which in turn increases the number of emitted electrons, assuming the frequency is above the threshold frequency.
Correct Answer: A — It doubles
Q. If the intensity of light is doubled while keeping the frequency constant, what happens to the number of emitted electrons in the photoelectric effect?
A.It doubles
B.It remains the same
C.It is halved
D.It becomes zero
Solution
Doubling the intensity of light increases the number of photons incident on the surface, which in turn increases the number of emitted electrons, assuming the frequency is above the threshold frequency.
Correct Answer: A — It doubles
Q. If the work function of a metal is 4.5 eV, what is the threshold wavelength for the photoelectric effect?
A.400 nm
B.500 nm
C.600 nm
D.700 nm
Solution
The threshold wavelength can be calculated using the equation λ = hc/φ. Substituting h = 4.14 x 10^-15 eV·s, c = 3 x 10^8 m/s, and φ = 4.5 eV gives λ ≈ 400 nm.
Correct Answer: A — 400 nm
Q. In a circuit with two inputs A and B, if A = 0 and B = 0, what is the output of an OR gate?
A.0
B.1
C.2
D.3
Solution
An OR gate outputs 1 if at least one input is 1. Since both inputs are 0, the output is 0.
Correct Answer: A — 0
Q. In a communication system, what does 'noise' refer to?
A.The desired signal
B.Unwanted disturbances that affect the signal
C.The modulation technique used
D.The bandwidth of the channel
Solution
Noise refers to unwanted disturbances that interfere with the desired signal, affecting the quality of communication.
Correct Answer: B — Unwanted disturbances that affect the signal
Q. In a communication system, what does 'signal-to-noise ratio' (SNR) measure?
A.The strength of the signal relative to background noise
B.The total power of the signal
C.The bandwidth of the communication channel
D.The efficiency of the modulation technique
Solution
Signal-to-noise ratio (SNR) measures the strength of the signal relative to the background noise, indicating the quality of the communication.
Correct Answer: A — The strength of the signal relative to background noise
Q. In a digital communication system, 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 frequency of the carrier wave
D.The duration of each bit
Solution
Bit rate refers to the number of bits transmitted per second in a digital communication system.
Correct Answer: A — The number of bits transmitted per second
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
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
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
Solution
The energy of the electron in the ground state of a hydrogen atom is -13.6 eV.
Correct Answer: A — -13.6 eV
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
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
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
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
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
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
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
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
Q. In a nuclear reaction, what is conserved?
A.Mass only
B.Charge only
C.Mass and charge
D.Energy only
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
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
Solution
The energy released when a nucleus is formed from its constituent nucleons is called binding energy.
Correct Answer: A — Binding energy
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
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
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
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
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
Solution
When a p-n junction diode is reverse-biased, the depletion region widens, preventing current flow.
Correct Answer: B — Depletion region widens
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
Solution
An electric field is formed at the p-n junction due to the diffusion of charge carriers.
Correct Answer: A — Electric field
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
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
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
Solution
The depletion region is the area around the p-n junction where charge carriers have recombined, leaving behind immobile ions.