The mirror at home has two reflecting surfaces, one is the upper surface of glass with weak reflection intensity, and the other is the inner surface of glass with high reflection intensity. We usually use the inner surface, that is, the silver-plated or aluminum-plated side.

The two beams of light reflected from the mirror can be regarded as two point light sources with the same frequency because of their different reflection points (one beam passes through the glass and the other beam does not pass through the glass), so interference fringes can be seen.

The change of incident angle means that the distance between two point light sources changes (you can see it by drawing a picture), and the position of the strong and weak points of coherence will also change.

The density of the ring decreases with the increase of the distance. Because the greater distance increases the "directional consistency" of the incident light, a larger angle is needed to make the reflected optical path difference and make the ring more sparse. I guess this is the case. I hope it can be explained.