Lenses and Image Formation | Physics | RRB NTPC Exam

Learn Lenses and Image Formation in Physics for the RRB NTPC Exam. In this lecture, Dharmendra Shukla explains the concepts of convex and concave lenses, image formation, lens formula, power of a lens, and magnification in a simple, exam-oriented manner. This video is useful for students preparing for RRB NTPC, Railway Group D, SSC, and other competitive examinations where basic Physics and Optics are important. Topics Covered in This Lecture Definition of a lens and refraction of light Inventors and history of lenses Types of lenses: Convex Lens and Concave Lens Convex lens properties, uses, and sign convention Image formation by a convex lens at different object positions Concave lens properties, uses, and applications Image formation by a concave lens Lens formula: 1/f = 1/v − 1/u Power of a lens and its SI unit, Diopter Magnification of lenses and image size Video Timeline / Chapters 00:00 – Introduction to Lenses 03:22 – Inventors of the Lens 04:10 – Types of Lenses 05:16 – Convex Lens: Properties and Uses 14:20 – Image Formation by a Convex Lens 23:30 – Concave Lens: Properties and Uses 31:13 – Image Formation by a Concave Lens 33:17 – Lens Formula 34:44 – Power of a Lens and Diopter 37:44 – Magnification of Lenses Important Physics Formulas Lens Formula: 1/f = 1/v − 1/u Power of a Lens: P = 1/f (when focal length is measured in metres) Magnification: m = Image Height / Object Height Remember: The power of a convex lens is generally positive, while the power of a concave lens is generally negative, using the standard Cartesian sign convention. Who Should Watch This Video? RRB NTPC aspirants Railway Group D candidates SSC exam aspirants Students revising basic Physics and Optics Competitive exam candidates preparing for questions on lenses and image formation Watch the complete lecture to understand lens concepts, remember 📚 Free Course Playlist for NTPC Exam:    • RRB NTPC 2026 Complete Course | GK, Maths,...   👉 Subscribe for regular Railway exam preparation videos.