JEE Physics - MCQ Practice Questions

Reverse bias strengthens the electric field across the junction, causing the depletion region to expand as more charge carriers are pulled away from the junction.

The current gain β is the ratio of collector current to base current (I_c/I_b). For silicon transistors, typical β values range from 50 to 500.

Silicon has dominated modern rectifiers because of significantly lower reverse saturation current (leakage ~nA at room temperature vs ~µA for Ge), better temperature stability, and superior thermal properties. The extra 0.4V drop is offset by reduced losses in high-power applications.

Using v = fλ, where v = 300 m/s and f = 150 Hz, λ = v/f = $\frac{300}{150}$ = 2 m

In transverse waves, particle oscillation is perpendicular to the direction of wave propagation, such as in electromagnetic waves and ripples on water

In constructive interference, phase difference is 0° or 2πn. Resultant amplitude = A₁ + A₂

For a string fixed at both ends, fₙ = nf₁ where n is the harmonic number. Second harmonic (n=2) has f₂ = 2f₁

Standing waves result from the superposition of two coherent waves traveling in opposite directions with the same frequency

Wave velocity v = √(T/μ), where T is tension and μ is mass per unit length. It is independent of frequency and amplitude

In longitudinal waves, particles oscillate parallel to the direction of wave propagation, creating compressions and rarefactions

Using v = fλ, we get λ = v/f = $\frac{20}{50}$ = 0.4 m

Beat frequency = |f₁ - f₂| = |256 - 260| = 4 Hz

From y = Asin(ωt - kx), ω = 2π/0.04 = 50π, k = 2π/0.8 = 2.5π. v = ω/k = 50π/2.5π = 20 m/s

λ = v/f = $\frac{330}{440}$ = 0.75 m

For a point source, intensity spreads over a sphere of area 4πr², so I ∝ 1/r²

At nodes, particles do not move. Amplitude of oscillation is zero, hence particle velocity is always zero

Energy E ∝ A² for harmonic waves. Kinetic energy = ($\frac{1}{2}$)mω²A²sin²(ωt)

Using v = fλ, we get λ = v/f = $\frac{20}{50}$ = 0.4 m

n = c/v = (3×10⁸)/(2×10⁸) = 1.5

For constructive interference, A_resultant = A₁ + A₂ = 3 + 4 = 7 units