JEE Physics - MCQ Practice Questions

Using Doppler formula: f' = f(v + v_observer)/v = 500(340 + 20)/340 = 529.4 Hz

At equidistant points, path difference = 0, hence phase difference = 0°. This leads to constructive interference

Using Doppler formula: f' = f × v/(v + v_source) = 600 × 340/(340 + 30) = 547 Hz

f₁ = ($\frac{1}{2}$L)√(T/μ) where μ = 0.$\frac{01}{1}$ = 0.01 kg/m. f₁ = 0.5 × √($\frac{40}{0}$.01) = 31.6 Hz

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

Diffraction is more prominent when wavelength is comparable to or larger than the aperture size

From y = A sin(2πx/λ - 2πt/T), we get λ = 4 m and T = 0.5 s. v = λ/T = $\frac{4}{0}$.5 = 8 m/s

In the second harmonic (n=2), f₂ = 2f₁. Therefore, f₁ = f₂/2 = $\frac{200}{2}$ = 100 Hz

Beat frequency = |f₁ - f₂| = |250 - 254| = 4 Hz

Using Snell's law: n₁sin(θ₁) = n₂sin(θ₂). 1.5 × sin(30°) = 1 × sin(θ₂). θ₂ = 48.75°

From y = A cos(kx) sin(ωt), we have k = π, so λ = 2π/k = 2π/π = 2 cm

# Solution: Organ Pipe Resonance Frequencies

For a pipe closed at one end, only odd harmonics can resonate due to boundary conditions at the closed end.

Step 1: Identify the Resonance Pattern for Closed Pipe

A pipe closed at one end has a node at the closed end and an antinode at the open end. This allows only odd multiples of the fundamental frequency to resonate.

Step 2: Calculate the Next Possible Resonance

The fundamental frequency (n = 1) is given as 200 Hz. The next possible resonance occurs at n = 2, which is the 3rd harmonic.

The frequency of the next possible resonance is 600 Hz.

The answer is (D) 600 Hz.

Sound intensity decreases with the square of the distance from a point source due to spherical spreading of the wavefront.

Step 1: Identify the Inverse Square Law

For a point source radiating uniformly in all directions, the intensity at distance r is inversely proportional to r². The power remains constant, but spreads over an increasing spherical surface area.

Step 2: Apply the Relationship Between Two Distances

We know intensity at r₁ = 1 m is I₁ = 10⁻⁸ W/m², and we need intensity at r₂ = 10 m.

The intensity at 10 m distance is 10⁻¹⁰ W/m². Answer: (A)

When a wave reflects from a fixed (denser) end, it undergoes a phase change of π radians or 180°

From y = 0.02sin(50πt - 4πx), comparing with y = Asin(ωt - kx): ω = 50π rad/s, k = 4π rad/m. Wavelength λ = 2π/k = 2π/(4π) = 0.5 m. Wave velocity v = ω/k = 50π/(4π) = 12.5 m/s.

A resonance tube with water acts as a closed pipe at the water surface and open at the top, requiring the air column length to be an odd multiple of λ/4 for resonance, but the effective length includes end correction beyond the physical opening.

Step 1: Calculate Wavelength

[The wavelength of sound in air is found using the wave equation with given frequency and speed.]

Step 2: Determine Condition for First Resonance

[For a closed pipe (water surface acts as closed end), first resonance occurs at the shortest air column length, which is λ/4.]

Step 3: Account for End Correction

[The effective length of the air column is greater than the physical length because sound appears to resonate beyond the open end by approximately 1 cm due to end correction.]

Final Answer: (C) 17.2 cm; due to end correction of approximately 1 cm for the open end

The effective length accounts for the fact that the sound wave's effective vibrating column extends slightly beyond the physical opening of the tube at the open end.