So my question is light travel as wave, so light energy is basically increasing and decreasing electric and magnetic field? How do I visualize it?
A very short answer, followed by a suggestion.
I can only tell you how I visualise it in wave terms, which is the standard textbook model, but I don't think there is a better way of describing it.
A static picture of an electromagnetic wave is:
The electromagnetic waves that compose electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. This diagram shows a plane linearly polarized EMR wave propagating from left to right. The electric field is in a vertical plane and the magnetic field in a horizontal plane. The electric and magnetic fields in EMR waves are always in phase and at 90 degrees to each other.
My suggestion is that you look at these images, and read the Wikipedia article, then post a more specific question on what aspects of the visualisation you don't follow.
Imagine throwing a stone in a pond. You'll now see waves moving away from where the stone dropped. A pond is a 2D plane, while EM waves travel in 3D. It would behave much like in the pond, but the waves would move away from the source in a spherical way.
The field is increasing and decreasing so theoretically the beam/field of light should have observable dark and light spots. We cannot see this because the frequency of light is roughly 500 THz.
It would be an interesting experiment to proof that these dark spots exist because if they don't, our theory of light and electromagnetism is wrong.
- In the above pictures there is drawn only the half of the electric and magnetic field component of light. It would be better to draw the north and the south pole of the magnetic field component as well as the full potential difference between plus and minus of the electric field component.
- The amplitude of the electric and the magnetic field component of light was never measured. And the electric field of a charge is defined as infinitely extended. But for the definition of light as a wave the amplitude has to be defined. So the square of amplitude was interpreted as the intensity of the given light. And the infinity was explained by the way, that light is a disturbance of an overall existing EM field.
- The phase dependence of the electric and the magnetic field components - their shift or no shift - for a laser beam as well as for single photons (if one think in photons) was never measured. For radio waves, which one make from accelerated electrons and by this made by a huge number of photons, for the reasons of discovered EM induction the electric field of the accelerated electrons in the antenna rod bear a magnetic field and this field bear an electric field and so on.
Following this points a sketch of a radio wave in the near field has the next form:
It is from some interest to show what is the discovery property of spin for an EM wave. It could be seen from the last sketch that there is a asymmetry in the relation between the directions of the electric und the magnetic field component. The blue and red arrows (representing the magnetic B-field and the electric E-field) follow each other anti-clockwise if one have a look in the direction of propagation. There is exactly one other possibility of arrangement of the field components. This shown in the second sketch:
For more clearness of what is an EM radiation, a photon and a radio wave see What is the relation between electromagnetic wave and photon?.