In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu `alaykum wa-rahmatullāhi wa-barakātuh.
If a person joins the Iman while the Imam is still in ruku he has attained that rakat. [i]
One who comes late and misses only Surah Faatiha he has not missed the rakat.
Since you are from India, it is quite possible that you are a follower of the Hanafi Mazhab (school of thought). Although you are in Oman, you should still follow the Hanafih Madhab.
And Allah knows best.
Mufti Saeed Ahmed Golaub
Islamic Solutions
Jamaica
[i]السنن الكبرى للبيهقي (2 / 128):
2580 - وَأَخْبَرَنَا أَبُو بَكْرِ بْنُ الْحَارِثِ الْفَقِيهُ، أنبأ أَبُو مُحَمَّدِ بْنُ حَيَّانَ، ثنا إِبْرَاهِيمُ بْنُ مُحَمَّدِ بْنِ الْحَسَنِ، ثنا أَبُو عَامِرٍ مُوسَى بْنُ عَامِرٍ، ثنا الْوَلِيدُ يَعْنِي ابْنَ مُسْلِمٍ، أَخْبَرَنِي مَالِكٌ، وَابْنُ جُرَيْجٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ أَنَّهُ كَانَ يَقُولُ: " مَنْ أَدْرَكَ الْإِمَامَ رَاكِعًا، فَرَكَعَ قَبْلَ أَنْ يَرْفَعَ الْإِمَامُ رَأْسَهُ، فَقَدْ أَدْرَكَ تِلْكَ الرَّكْعَةَ "