If the speed of light is taken as 3 × 10⁸ m/s, its value in scientific notation with three significant figures is: MCQ with Answer and Explanation

Explanation:
Lens maker's formula: 1/f = (μ_lens/μ_medium - 1)(...). In water, relative refractive index reduces, so power decreases, focal length increases. Glass in water behaves less converging.

Explanation:
Sound waves are mechanical, require medium.

Explanation:
Inside a long solenoid, magnetic field is uniform (constant magnitude and direction), parallel to the axis, given by B = μ₀nI, where n is turns per unit length. Outside, field is nearly zero. This uniformity makes solenoids useful for creating controlled magnetic fields. Memory tip: 'Solenoid: uniform B inside like bar magnet'. This conceptual question tests knowledge of magnetic field configurations, crucial for electromagnetism in competitive exams. Always distinguish solenoid field (uniform inside) from straight wire field (circular, non-uniform).