General Science - MCQ Practice Questions

In beta-minus decay, a neutron converts to a proton, emitting an electron (beta particle) and an antineutrino. This increases atomic number by 1.

Rayleigh scattering causes shorter blue wavelengths to scatter more effectively than longer red wavelengths when sunlight passes through the atmosphere, making the sky appear blue.

Period T = 2π√(m/k) = 2π√($\frac{5}{200}$) = 2π√($\frac{1}{40}$) = 2π × (1/(2√10)) = π/√10 ≈ π s (approximately).

Using P = V²/R, we get R = V²/P = (250)²/1000 = $\frac{62500}{1000}$ = 62.5 Ω.

Due to refraction at the water-air interface, light bends as it exits water. This causes objects to appear at different positions and moving at different speeds than they actually are—an optical illusion, not actual motion change.

From orbital mechanics: v = √(GM/r). If r becomes 2r, then v_new = √(GM/2r) = v/√2. Velocity decreases by factor √2.

# Photoelectric Effect - Maximum Kinetic Energy

The photoelectric effect describes how photons transfer their energy to electrons in a metal, with excess energy becoming kinetic energy after overcoming the work function barrier.

Step 1: Calculate the Energy of the Incident Photon

The energy of a photon is determined by its frequency using Planck's equation.

Step 2: Convert Photon Energy to eV

Convert joules to electron volts using the given conversion factor.

Step 3: Apply Einstein's Photoelectric Equation

The maximum kinetic energy equals the photon energy minus the work function (threshold energy).

The maximum kinetic energy of the photoelectron is 0.07 eV.

Answer: (A) 0.07 eV

Acoustic impedance (Z) = ρ × c, where ρ is density and c is sound velocity. SI unit is kg/(m²·s). It's crucial for understanding sound reflection and transmission.

Electric potential is defined as work done per unit charge. SI unit is Joule/Coulomb = Volt. Option D (Watt/Ampere) also equals Volt but option A is more fundamental.

Using lens formula: 1/f = 1/u + 1/v. $\frac{1}{15}$ = $\frac{1}{30}$ + 1/v gives v = 30 cm. When u = 2f, image forms at 2f with magnification -1 (same size, inverted, real).

At sunset, light travels through a longer path in the atmosphere. Shorter wavelengths (blue) scatter more (Rayleigh scattering), leaving longer wavelengths (red) to reach the observer.

This problem uses the kinematic equation relating velocity, acceleration, and time for motion starting from rest.

Step 1: Identify the Given Values

We are given the initial velocity (starting from rest), final velocity, and acceleration. We need to find the time taken.

Step 2: Apply the Kinematic Equation

Using the equation that relates final velocity, initial velocity, acceleration, and time:

Substituting the values:

The car takes 10 seconds to reach 20 m/s. The answer is (B) 10 seconds.

Gravitational force is always attractive, acts between any two masses, is independent of the medium, and is governed by Newton's law of universal gravitation.

When object distance (5 cm) < focal length (10 cm), the object is between the mirror and focus. A concave mirror forms a virtual, erect, and magnified image in this case.

For parallel resistances: 1/R = 1/R₁ + 1/R₂ = $\frac{1}{10}$ + $\frac{1}{20}$ = $\frac{3}{20}$. Therefore R = $\frac{20}{3}$ = 6.67 Ω.

Using v = fλ, where v = 330 m/s and f = 440 Hz. λ = v/f = $\frac{330}{440}$ = 0.75 m.

Elastic potential energy E = ($\frac{1}{2}$)kx². 5 = ($\frac{1}{2}$)k(0.1)². 5 = 0.005k. k = 1000 N/m.

The photoelectric effect occurs when light of frequency greater than or equal to the threshold frequency strikes a metal surface, causing electron emission. It demonstrates the particle nature of light.

Kinetic energy KE = ($\frac{1}{2}$)mv². When velocity is doubled: KE' = ($\frac{1}{2}$)m(2v)² = ($\frac{1}{2}$)m(4v²) = 4 × ($\frac{1}{2}$)mv² = 4K.

The Second Law of Thermodynamics states that entropy of an isolated system increases or remains constant. Heat spontaneously flows from hot to cold, not vice versa, establishing the direction of processes.