what is the expected question in ray optics NEET 2020 exam ,and which concept??

Harsha, it is difficult to pick questions from topics. A look at the previous question papers can help you in regards to this. We cannot help you with the questions that might come in the exam but can help you with the weightage of each Chapter.

In Physics, Highest weightage goes to Optics at 10%. Thermodynamics, Electrostatics, Electronic devices share 9%. Current Electricity and Electromagnetic induction, Alternating current take 8%. Dual Nature of Radiation gets 6% while Motion systems of rigid particles and body and Magnetic effects of Currents, Electromagnetic waves and Magentism get 5%. Work, Energy and Power take 4%, Atoms and nuclei, Oscillation and Waves, Properties of Bulk Matter, Laws of Motion and Kinematics share 3% and the rest of the topics carry 2% weightage.
10% is 6-7 questions, 9% is 4-5 questions, 7% is 3 questions, 4- 5% is 2 questions , 2-3% is 1 question.
In Chemistry, Coordination points get 9% of weightage. Thermodynamics takes the 8% and Equilibrium takes the 6% weightage slots respectively. Chemical Bonding and Organic structure carries the 5% weightage slot and rest of the topics carry 2-3% weightage in the exam paper.
10% is 6-7 questions, 9% is 4-5 questions, 6-7% is 3 questions, 4- 5% is 2 questions , 2-3% is 1 question.
In Biology, Diversity of Living Organisms has 14% weightage. Structural Organisationi n Plants and Animals takes 5%. Plant Physiology has 6% and Cell Structure and Function has 9%. Human Physiology has 20% weightage. Reproduction chapter has 9% and Genetics and Evolution has 18% weightage. Biology and Human Welfare has 9% weightage. Biology and its application has 4% weightage and Ecology and Environment has 6% weightage
18-20% is 15-20 questions, 12- 14% is 10 questions, 10% is 6-7 questions, 9% is 4-5 questions, 6-7% is 3 questions, 4- 5% is 2 questions , 2-3% is 1 question.
This is an observation based on previous years question papers.