Chemistry is not any criteria to get into NDA . actually chemistry is part of NDA/Na 's second paper known as gat(general adaptability test ) which is conducted by upsc . Gat is divided into two sections first one consist 50 question of english comprises synonyms , antonyms , idioms,passage reading ,spotting error. Second part comprises question of history , geography,polity,physics , chemistry, polity , current affairs now it has been cleared that chemistry is not any criteria for nda but it is part of paper but as u asked necessary ,so yes it is necessary if u want to score high marks in gat paper because it's contribution in paper is 20 to 25 question .so yeah it becomes necessary for candidate to prepare well in order to score high.

NDA Physics Syllabus

The following topics are included in the Physics section of NDA :

Mass, Force and Momentum, Gravitation, Sound waves and their properties, Natural and Artificial Magnets, Measurement of Electrical Power, Weight, Motion of objects, Power and Energy, Change of State and Latent Heat, Spherical mirrors and Lenses, Conductors and Non-conductors, Density, Velocity and Acceleration, Effects of Heat, Modes of transference of Heat, Properties of a Magnet, Lighting and Magnetic effects of Current, Volume, Principle of Archimedes, Newton’s Laws of Motion, Parallelogram of Forces, elementary ideas of work, Measurement of temperature and heat, Rectilinear propagation of Light, Human Eye, Earth as a Magnet, Primary and Secondary Cells, Specific Gravity, Pressure Barometer, Stability and Equilibrium of bodies, Reflection and refraction, Heating, Simple musical instruments, Use of X-Rays, Static and Current Electricity, Ohm’s Law Simple Electrical Circuits.

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