Wave Optics: Electromagnetic Waves

[Prannoy Mehta]

" Thus according to Maxwell, light waves are associated with changing electric and magnetic fields; changing electric field produces a time and space varying magnetic field and a changing magnetic field produces a time and space varying electric field. The changing electric and magnetic fields result in the propagation of electromagnetic waves even in vacuum" - NCERT Physics Grade XII.

What does the term time and space varying electric field/magnetic field mean ?

 

[mfb]

The fields vary both in space (they are not the same everywhere) and time (they are not the same forever).

 

[sophiecentaur]

That's a bit much for a single post, I think.
The answer 42 springs to mind.

What is your level of Science education? EM is a vast topic and best approached from some very basic ideas, based on well known phenomena. The presence of a force in the region of a charged object or a magnet can be conveniently 'explained' in terms of a Field (region of influence), in the same way that our weight can be explained in terms of the Earth's g 'Field'.
A Field doesn't have to be looked upon as 'real'- just an aid to calculating and predicting effects. We are only aware of such a Field by its effect on objects and there are alternative ways of explaining such forces which don't necessarily involve the Field idea. But the Field approach has proved to be very powerful.