A 0.1 eV
B 1.1 eV
C 3.0 eV
D 5.0 eV
Explanation: Silicon has a band gap of about 1.1 eV at room temperature, making it a semiconductor.
A V₀I₀/2
B V_rms × I_rms × cos φ
C V₀I₀
D V_rms × I_rms
Explanation: Average power = V_rms I_rms cos φ, where φ is the phase angle between voltage and current.
A Maximum
B Minimum (equal to R)
C Zero
D Infinite
Explanation: At resonance, XL = XC, so impedance Z = √(R² + (XL-XC)²) = R (minimum value).
A R/ωL
B ωL/R
C 1/RC
D R/ωC
Explanation: Q = ωL/R = 1/(ωCR) at resonance. Higher Q means sharper resonance.
A 2200 V
B 220 V
C 22 V
D 110 V
Explanation: Vs/Vp = Ns/Np → Vs = Vp × (Ns/Np) = 220 × (1/10) = 22 V (step-down transformer).
A 50%
B 75%
C 100%
D Depends on load
Explanation: An ideal transformer has no losses (no copper loss, no iron loss), so efficiency = 100%.
A Doubles
B Halves
C Remains same
D Quadruples
Explanation: Fringe width β = λD/d. If d is halved, β doubles.
A 1.22λ/D
B D/(1.22λ)
C λ/D
D D/λ
Explanation: Resolving power = D/(1.22λ), where D is the aperture diameter and λ is the wavelength of light used.
A Real and inverted
B Virtual, erect and magnified
C Real, erect and magnified
D Same size as object
Explanation: When object is between F and optical center of convex lens, image is virtual, erect, and magnified on the same side.
A 1 + D/f
B D/f
C f/D
D D/(D+f)
Explanation: For a simple microscope (magnifying glass), magnifying power M = 1 + D/f, where D is the least distance of distinct vision.
A Less than critical angle
B Equal to critical angle
C Greater than critical angle
D 90°
Explanation: TIR occurs when angle of incidence > critical angle when light travels from denser to rarer medium.
A 30°
B 42°
C 48.6°
D 60°
Explanation: sin ic = 1/μ = 1/1.5 = 0.667 → ic = sin⁻¹(0.667) ≈ 41.8° ≈ 42°
A Two isothermal and two adiabatic processes
B Four isothermal processes
C Two adiabatic and two isobaric processes
D Four adiabatic processes
Explanation: Carnot cycle: two isothermal (at TH and TL) and two adiabatic processes forming a reversible cycle.
A 100%
B Greater than 50%
C Less than 100%
D Zero
Explanation: Carnot efficiency η = 1 - TL/TH is always less than 100% unless TL = 0 K (impossible).
A Always decreases
B Always increases
C Remains constant
D Can increase or decrease
Explanation: Second law of thermodynamics: entropy of an isolated system always increases or remains constant in reversible processes.
A Fast
B Done at constant temperature
C Quasi-static and without friction
D Adiabatic
Explanation: A reversible process must be quasi-static (infinitely slow) and free from dissipative forces like friction.
A 7.25 × 10^14 Hz
B 1.34 × 10^15 Hz
C 9.0 × 10^14 Hz
D 4.8 × 10^14 Hz
Explanation: f₀ = φ/h = 3.0/(4.14 × 10⁻¹⁵) = 7.25 × 10^14 Hz
A 1.1 V
B 2.3 V
C 3.1 V
D 0.5 V
Explanation: E = hc/λ = (12400 eV·Å)/(4000 Å) = 3.1 eV. Vstop = E - φ = 3.1 - 2.0 = 1.1 V
A Frequency of light
B Intensity of light
C Wavelength only
D Work function only
Explanation: The number of photoelectrons is directly proportional to the intensity of incident light (number of photons).
A Increases with intensity
B Increases with frequency
C Is independent of frequency
D Decreases with intensity
Explanation: KE_max = hf - φ, so maximum kinetic energy increases linearly with frequency of incident light.