2 light beams at 90 degree?

Question

2 light beams head on will interfere constructively/destructively.

how do 2 lights beams 90 degrees to each other interact?

Answer 1

Corresponding components of the electric and magnetic fields of each beam will interfere at every point in space where the light beams intersect. For simplicity, assume that beams A and B are propagating in vacuum in the x and y directions, respectively. The electric and magnetic fields of A can be decomposed into components in the y and z directions. The electric and magnetic fields of B can be decomposed into components in the x and z directions. The z components common to both beams will interfere and the measured intensity will be the square of the electric field amplitude. If A and B are plane waves, the interference pattern will be symmetric about a plane inclined at 45 degrees to both incident beams.

Answer 2

Constructively
Light is based on packet emmisions called photons.
The end effect is that it excites what it falls on i.e. there is an increase in energy of the target it falls on.
The effect can be visualized in a stadium where the lights from various angles are focused on the players, making them and their actions clearly more visible to the audience.
Any ways energy cannot be cancelled out since there is no -ve energy(to the best of my knowlegde till date) it only adds up.
I don't think angle does much in the interaction of two light beams. However the effect of various angles on the target object depends upon the size of the object, nature of the light beam, nature of the object, its density, opaqueness etc.