There will be a virtual light on the side of a strong light. Does this virtual light only appear on one side or both sides? I hope the answer can be more detailed and professional.

Both sides will appear, just all the places where light and shade alternate will appear, which is caused by the diffraction of light. Since you said it was strong light, it means that the light encountered obstacles and was blocked in the process of propagation. When the light wave passes near the obstacle, it will spread more or less in a straight line due to the diffraction effect, so that part of the light will reach the original dark area nearby, forming what the subject calls "virtual light".

Ps: diffraction of light

The phenomenon that light waves will deviate from the linear propagation law in geometric optics more or less after encountering obstacles. Geometrical optics shows that light propagates in a uniform medium according to the law of straight line, while light propagates at the interface between two media according to the laws of reflection and refraction. However, light is electromagnetic wave. When a beam of light passes through a perforated fence, its intensity can spread to the geometric shadow area defined by the linear propagation law, which also makes some dark spots or dark lines appear in the geometric illumination area. In a word, the diffraction effect makes the light intensity distribution in the space behind the obstacle different from that given by geometric optics and when the light wave propagates freely, and the diffracted light intensity is redistributed. Diffraction makes all geometric shadow circles lose the edge of Ming Rui. The Italian physicist and astronomer F.M. grimaldi accurately described the diffraction phenomenon of light for the first time in the17th century. After 150 years, the French physicist A.-J. Fresnel first described it in the19th century.