Olympiads are tough examinations. The questions asked in Olympiads cover both 11th and 12th syllabus and their quality is much better than the JEE questions. You should definitely prepare for them with the primary motive being to solve a better set of problems. Do not prepare for Olympiads as if your life depends on them as no qualification might make you depressed, thus harming the preparation for your other exams.
Winning a medal however helps in getting international recognition. It helps in applying for foreign universities and certifies your superior quality of problem solving skills right at the high school level.NSEP – National Standard Examination in Physics
Almost all JEE syllabus is covered for the Physics Olympiad. Semiconductors, types of magnetism, communication are some areas which have to be focused. Problem solving speed plays an important role in the olympiads. Check out the previous years’ solved papers here.
NSEC – National Standard Examination in Chemistry
In the Chemistry Olympiad, questions cover a lot of information. Questions are from a variety of topics so you have to remember the things. The paper is easy scoring so the cutoff goes high. Previous years’ papers can be found here.
NSEA -National Standard Examination in Astronomy
Although this is named as Astronomy Olympiad, questions mainly come from Maths and Physics. Some topics play an important role such as gravitation, thermodynamics, blackbody radiation, mechanics. Students from class 11 can crack this olympiad as the maths questions are mostly from Class 11. Link for previous years’ questions.
Olympiads can be a test of JEE preparation. NCERT along with JEE syllabus is mostly sufficient for all the olympiads. Chemistry olympiads cover the entirety of JEE syllabus. Detailed information for each of these olympiads can be found in the official website.
If someone has performed well in the olympiads, it is an indication of his/her knowledge of the subjects besides proving the preparation level for the competitive entrance examinations.