Science Group
Explore subjects and practice MCQs
7
Chapters
1,610
Total MCQs
Science Group
Answer: At threshold frequency f₀, KE = hf₀ - φ = 0. The photon energy just equals the work function.
Answer: T = 2πm/qB is independent of both speed and radius. It depends only on m, q, and B.
Answer: Lenz\'s law gives the direction of induced current, while Faraday\'s law gives the magnitude of induced EMF.
Answer: Stefan-Boltzmann law: E = σT⁴. Energy radiated is proportional to the fourth power of absolute temperature.
Answer: λ = h/√(2qVm). λp/λα = √(qα/qp) = √(4e/e) = 2. So ratio is 2:1.
Answer: Δλ = (h/mc)(1-cos90°) = (h/mc)(1-0) = h/mc = 2.43 × 10⁻¹² m (Compton wavelength).
Answer: Beta particles have a continuous energy spectrum from 0 to a maximum value, because energy is shared with the antineutrino.
Answer: v = cα where α = e²/(4πε₀ℏc) ≈ 1/137 is the fine structure constant. So v ≈ c/137.
Answer: E₂ = E₁/2² = -13.6/4 = -3.4 eV. First excited state is n=2.
Answer: In a step-down transformer, voltage decreases but current increases (conservation of power: VpIp = VsIs).
Answer: Carbon in CH4 forms four sigma bonds with no lone pairs, giving sp3 hybridization and tetrahedral geometry.
Answer: Carbon-14 has atomic number 6 (protons = 6) and mass number 14. Neutrons = 14 - 6 = 8.
Answer: The azimuthal quantum number (l) determines the shape of an orbital: l=0 is s (spherical), l=1 is p (dumbbell), etc.
Answer: Oxygen has an electronegativity of 3.44 on the Pauling scale, which is higher than Na (0.93), Mg (1.31), and Cl (3.16).
Answer: Glucose is a monosaccharide with the molecular formula C6H12O6, containing six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.
Answer: NaCl is formed by the transfer of an electron from Na to Cl, creating Na+ and Cl- ions held together by electrostatic (ionic) forces.
Answer: In K2Cr2O7: 2(+1) + 2(Cr) + 7(-2) = 0, so 2Cr = 12, Cr = +6.
Answer: Charles\'s law states V ∠T (at constant P and n), meaning volume increases linearly with absolute temperature.
Answer: HCl is a strong acid that fully dissociates. [H+] = 0.001 M = 10^-3, so pH = -log(10^-3) = 3.
Answer: The configuration [Ar] 3d10 4s2 4p5 has 35 electrons, which corresponds to Bromine (Z = 35).