NDA & CDS 2 2025 Exam Physics Revision Class 1

Introduction

Physics is the study of nature and natural phenomena, expressed through laws, principles, and experiments. For aspirants preparing for the NDA CDS 2 (2025) examination, revising the fundamental topics of Units and Measurement and Reflection of Light is essential. These topics not only form the foundation of physics but also enhance analytical skills, accuracy, and logical understanding—qualities vital for defense aspirants.

Units and Measurement

Every physical quantity in physics can be expressed in terms of a numerical value and a unit. To ensure uniformity and clarity, the International System of Units (SI) is used worldwide.

1. Fundamental Quantities: These include length (metre), mass (kilogram), time (second), electric current (ampere), temperature (kelvin), luminous intensity (candela), and amount of substance (mole).
2. Derived Quantities: Formed by combining fundamental quantities, e.g., velocity (m/s), force (newton), and energy (joule).
3. Measurement: The process of comparing a physical quantity with a standard unit. Precision and accuracy in measurement are crucial, as errors may arise in observation, instruments, or methods.
4. Significant Figures: These indicate the precision of measured values and help in maintaining uniformity in calculations.

A strong grasp of this topic ensures accuracy in numerical problem-solving, which is heavily tested in NDA exams.

Reflection of Light

Light is a form of energy that enables us to see objects. When light falls on a surface, it may be reflected, absorbed, or transmitted. The study of reflection of light is essential for understanding optics.

1. Laws of Reflection:
   • The incident ray, reflected ray, and normal to the surface all lie in the same plane.
   • The angle of incidence is equal to the angle of reflection.
2. Types of Reflection:
   • Regular Reflection: Occurs on smooth surfaces like mirrors, giving clear images.
   • Irregular Reflection: Occurs on rough surfaces, scattering light in different directions.
3. Plane Mirrors: Form virtual, erect, and laterally inverted images of the same size as the object.
4. Spherical Mirrors:
   • Concave Mirror: Can form real or virtual images depending on object position, used in headlights, torches, and shaving mirrors.
   • Convex Mirror: Always forms virtual, erect, and diminished images, commonly used as rear-view mirrors in vehicles.

Understanding reflection is vital not only for examinations but also for practical applications in defense equipment, optics, and navigation.

Conclusion

The topics of Units and Measurement and Reflection of Light provide a strong foundation for deeper concepts in physics. While units and measurement sharpen problem-solving accuracy, reflection of light develops conceptual clarity in optics. For NDA CDS 2 (2025) aspirants, mastering these topics ensures confidence in both theoretical and numerical sections of the examination. A disciplined approach to revision and practice will undoubtedly lead to success.