The working of an optical fibre is based on MCQ with Answer and Explanation

Explanation:
Michael Faraday discovered electromagnetic induction (1831): changing magnetic flux induces EMF. Oersted found current-magnetism link; Ampere studied forces; Volta invented battery. Memory aid: 'Faraday = induction; Lenz = induced current direction'. History-based question testing key discoveries, frequently appearing in competitive exams.

Explanation:
Resolving power (minimum resolvable distance) d = λ/(2NA), where NA is numerical aperture. Oil immersion increases NA by matching refractive index between slide and objective, reducing light refraction and increasing light collection. Longer wavelength (A) decreases resolving power; decreasing NA (C) worsens resolution; magnification (D) doesn't affect fundamental resolution limit. Memory aid: 'Higher NA or shorter λ ⇒ better resolution'. This application question tests optical instrument knowledge, common in competitive exams. Always link resolution to wave nature of light (diffraction limit) and instrument design factors.

Explanation:
Astigmatism: cornea curvature not spherical, different focal lengths in different planes. Corrected by cylindrical lens which has different powers in perpendicular axes. Not simple spherical lens.