FBISE Class 9th (SSC-l)
Explore subjects and practice MCQs
3
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1,610
Total MCQs
FBISE Class 9th (SSC-l)
Answer: In beta minus decay, a neutron converts to a proton, emitting an electron and antineutrino.
342
Answer: Gamma rays are high energy electromagnetic photons emitted during nuclear transitions.
Answer: λ = ln2/t½. The decay constant and half-life are inversely related.
Answer: Activity can be measured in Becquerel (SI), Curie, or Rutherford units. 1 Ci = 3.7 × 10^10 Bq.
Answer: Forward bias: p-side connected to positive terminal, n-side to negative, reducing the barrier potential.
Answer: Silicon has a band gap of about 1.1 eV at room temperature, making it a semiconductor.
Answer: Average power = V_rms I_rms cos φ, where φ is the phase angle between voltage and current.
Answer: At resonance, XL = XC, so impedance Z = √(R² + (XL-XC)²) = R (minimum value).
Answer: Q = ωL/R = 1/(ωCR) at resonance. Higher Q means sharper resonance.
350
Answer: Vs/Vp = Ns/Np → Vs = Vp × (Ns/Np) = 220 × (1/10) = 22 V (step-down transformer).
Answer: An ideal transformer has no losses (no copper loss, no iron loss), so efficiency = 100%.
Answer: Fringe width β = λD/d. If d is halved, β doubles.
Answer: Resolving power = D/(1.22λ), where D is the aperture diameter and λ is the wavelength of light used.
Answer: When object is between F and optical center of convex lens, image is virtual, erect, and magnified on the same side.
Answer: For a simple microscope (magnifying glass), magnifying power M = 1 + D/f, where D is the least distance of distinct vision.
Answer: TIR occurs when angle of incidence > critical angle when light travels from denser to rarer medium.
Answer: sin ic = 1/μ = 1/1.5 = 0.667 → ic = sin⁻¹(0.667) ≈ 41.8° ≈ 42°
Answer: Carnot cycle: two isothermal (at TH and TL) and two adiabatic processes forming a reversible cycle.
Answer: Carnot efficiency η = 1 - TL/TH is always less than 100% unless TL = 0 K (impossible).
Answer: Second law of thermodynamics: entropy of an isolated system always increases or remains constant in reversible processes.