In a tungsten filament lamp, electrons travel through a high resistance path,due to which the temperature is increased. Now why does it emit light , is it because of the transitions of electrons from one energy state to another or is it radiation because of temperature. And are these two related in any way?Does light from a heated object has different reasons than the light from transitions?And also if electrons are ionised already how are the transitions happening?
Light from electron transitions between energy levels in an atom is fundamentally different from light emitted by hot objects. Any specific transition produces light that is of one frequency (color) only or nearly so and is called a line spectrum. Because the energy difference between the two levels in that transition is the same every time a transition occurs and is the same for every atom of that substance, only a single frequency of light gets emitted.
The light emitted from a hot object is in the form of a continuous spectrum that contains a broad spread of frequencies, and is called blackbody radiation. It arises because electromagnetic radiation can interact with hot atoms in a substance and energy can get shared back and forth between the radiation and the atoms across a range of possible frequencies.
In the case of a light bulb filament, the electrons that are being forced to flow through it are impeded by faults and obstructions in the crystalline structure of the metal and therefore transfer energy to the crystal lattice, causing the atoms in it to vibrate about randomly. Those random vibrations represent heat, and the filament gets hot enough to begin emitting a black body spectrum that contains visible light.