Physics

Diffraction is more pronounced at sharp edges than at rounded edges. A sharp edge causes an abrupt truncation of the wavefront, generating strong diffraction effects such as pronounced bending and interference patterns. Rounded edges provide a smoother transition for waves, reducing the abruptness of the wavefront disturbance and thus decreasing the diffraction effect. This is supported by practical examples such as speaker cabinet design, where rounding edges reduces diffraction-related sound distortions, typically by about 1 dB in the mid-high frequency range.

Cleavage is the property of crystals to break along specific planes of weakness, resulting in smooth, flat surfaces. This is a characteristic feature distinguishing cleavage from other properties like symmetry or isotropy.

Escape velocity from a celestial body can be calculated using the formula v = sqrt(2gr), where g is the acceleration due to gravity on the surface and r is the radius of the body. Given g = 1.6 m/s² and r = 1600 km = 1,600,000 m, the escape velocity is v = sqrt(2 × 1.6 × 1,600,000) = sqrt(5,120,000) ≈ 2263 m/s or about 2.26 km/s. This matches option D (2263 m/s). The originally stated correct answer (C) is incorrect. The explanation in the question also correctly calculates the escape velocity but mistakenly identifies option D as correct while the answer key says C. The correct answer is D.

Friction is a non-conservative force because it dissipates mechanical energy as heat, unlike electric, gravitational, and magnetic forces which are conservative and conserve mechanical energy in a closed system.

Work done is force times distance. Both lift weights through the same distance, but the man lifts a heavier weight, so he does more work. However, power is work done per unit time. The child lifts a lighter weight but does it much faster, resulting in greater power output. Thus, the child does more work per second (more power).

Two light sources are considered coherent if they emit waves of the same wavelength and maintain a constant phase difference, which is essential for producing stable interference patterns.

When a light ray travels from a rarer to a denser medium and reflects, it undergoes a phase change of 180° (or π radians). This is a fundamental concept in wave optics related to phase shifts upon reflection.

Escape velocity is the minimum speed needed for an object to escape from the gravitational field of a body without further propulsion. It depends on the mass and radius of the Earth (or the central body) and the gravitational constant, but it is independent of the mass of the escaping object. The angle at which the object is thrown affects the trajectory but not the minimum speed required to escape. Therefore, the escape velocity is independent of the object's mass, making option A correct.

The work done against gravity when raising a body is calculated using the formula W = m × g × h, where m is the mass, g is the acceleration due to gravity (approximately 9.81 m/s²), and h is the height raised. For a mass of 2 kg raised through 2 meters, the work done is W = 2 × 9.81 × 2 = 39.24 J, which rounds to 39.2 J. Therefore, the correct answer is option C (39.2 J). The originally given option A (38.2 J) is incorrect as it does not match the calculation.

A wave front is defined as the locus of all points in a medium that have the same phase of vibration, meaning they oscillate together. This matches the definition given in the question, making option D correct.