Question

if electrons emits energy continuously then why we observe line spectrum

Answer 1

electrons do not emit energy coz they move in their energy levels known as orbits.
if they are supplied with high energy they move to the subsequent energy shell and when they come back to their original shells they emit light rays known as spectral lines. this concept was given by neil bhor for hydrogen like atoms.............hope it will help u

Answer 2

Haha ! Gud question . Well , Rutherford also first thought that electrons emit out energy continuously , & due to this Many scientists Neglected or You can say , wrong postulate said by Rutherford , if it is so , then a time will come , when electron will emit out its all energy & got distroyed or fall into the nucleus , but atom is stable , its the observation , have you ever observed your pen or pencil got distroyed automatically ? No na , So , Bohr said that , its not like that , they dont emit out energy , actually , electrons have their orbits & in these orbits they revolve & electron have its energy level , when it got some extra energy , like heat , it got excited & went to high energy level , & when it comes down again it emits out energy , it can be of any form heat or light