Introduction
Light is one of the most important topics in Physics for NDA and CDS examinations because it directly connects basic physical principles with everyday phenomena. The chapters Reflection of Light, Refraction of Light, and Human Eye and the Colourful World together explain how light behaves when it strikes surfaces, passes through different media, and interacts with the human eye and atmosphere.
These concepts form the foundation of optics, which is frequently tested in NDA and CDS exams through numerical problems, ray diagrams, conceptual MCQs, and application-based questions. Understanding these topics not only helps in scoring well in the exam but also improves scientific reasoning, which is essential for defence aspirants.
1. Reflection of Light
Reflection of light explains how light rays bounce back when they strike a smooth or polished surface such as a plane or spherical mirror. The laws of reflection, formation of images, and characteristics of images formed by plane, concave, and convex mirrors are key areas of focus.
For NDA/CDS MCQs, emphasis is placed on:
- Laws of reflection
- Ray diagrams
- Image formation by concave and convex mirrors
- Mirror formula and magnification
- Applications in daily life (rear-view mirrors, shaving mirrors, etc.)
2. Refraction of Light
Refraction of light deals with the bending of light when it passes from one medium to another due to a change in speed. This topic introduces important concepts such as refractive index, Snell’s laws, and refraction through glass slabs and lenses.
Important areas for exams include:
- Laws of refraction
- Refractive index and its relation with speed of light
- Refraction through rectangular glass slab
- Image formation by convex and concave lenses
- Lens formula and magnification
Numerical problems from refraction are high-scoring and frequently repeated in NDA and CDS exams.
3. Human Eye and the Colourful World
This chapter connects physics with biology and environmental science. It explains the structure and working of the human eye, vision defects, and their correction using lenses. It also covers fascinating natural phenomena such as dispersion of light, scattering of light, rainbow formation, and atmospheric effects.
Key exam-relevant concepts include:
- Defects of vision (myopia, hypermetropia, presbyopia)
- Correction using lenses
- Dispersion of light and spectrum
- Scattering of light (why sky is blue, sun appears red at sunrise/sunset)
- Formation of rainbow
These topics are commonly asked as conceptual MCQs.
Importance for NDA & CDS 1, 2026 Examination
- Questions from Light are almost guaranteed in NDA and CDS Physics sections.
- Most questions are direct, concept-based, and numerical, making them easy to score with proper practice.
- Ray diagrams, formulas, and real-life applications are frequently tested.
- Strong command over this chapter can help aspirants secure quick and accurate marks.
Conclusion
The chapters Reflection of Light, Refraction of Light, and Human Eye and the Colourful World together form a complete and essential unit for NDA and CDS Physics preparation. These topics not only strengthen conceptual understanding but also develop problem-solving skills required for competitive examinations.
For NDA & CDS 1, 2026, aspirants should focus on clear concepts, formula application, ray diagrams, and repeated MCQ practice. Mastery of these chapters ensures confidence in the Physics section and contributes significantly to overall exam performance.
Consistent revision and solving previous years’ questions from these topics can make Light one of the most scoring areas in NDA and CDS examinations.
