Abstract: In this paper，a simple and natural reasoning method is used to deduce the virtual image

point posi- tion of the secondary refraction imaging of object point refracting through the

parallel medium interface，and the so- called “superposition rule of refraction imaging of object

points through multi-layer parallel medium interface”is found. This paper discusses the

coordinates of image points in several special cases: the refraction phenomenon of “body

head separation”of the female swimmer in swimming pool is analyzed and explained; the imaging

character- istics of objects in the air through glass blocks are analyzed，the optical basis

for people to usually use thin glass windows is pointed out; the refraction imaging of an

object point in air through a medium with linear refractive index change is studied in detail，and

it is pointed out that the position of the imaging point in the medium with uniformly varying

refractive index is almost the same as that in the medium with uniform refractive index of

same thickness， except for the large angle of view from 80° to 90°. The reasoning methods and

conclusions in this paper may provide reference for the teaching and scientific research of related

contents.

Key words: object point, parallel medium interface, refraction imaging, superposition rule , linear change of refractive index