Q: If an imam recites the 1st 15 verses (i.e. 1st ruku) from (1-15) of Surah Maryam in his 1st rakaat of fajr salah and in his second rakat recites 25 verses (i.e 2nd ruku) from 16-40, is the salaah valid?
A: Yes, the namaaz will be valid. However, to have the second rakaat longer than the first is makrooh.
The namaaz is valid. Namaaz behind him will also be valid.
And Allah Ta’ala (الله تعالى) knows best.