The Whenever a light ray reaches a surface and refracts, part of the light will be partially reflected. This means that only some of the light energy successfully passes into the other medium; some of the light energy is always reflected.

A partial reflection is a reflection and so obeys the laws of reflection.

 

This is observed when you stand next to a window (especially for a shop window if the shop is closed and the lights are off inside) and you see a reflection of yourself in the window.

In this photo (and the closeup section below) you will see my reflection as I take a picture of the building from the outside.

In general, the larger the incident angle the larger the proportion of light that gets reflected.

In this image light from the mountain hits the lake at a large angle of incidence. Thus apart from the light refracting into the water a significant percentage of the light will be reflected (partial reflection) giving the image of the mountain in the lake.

You are not required to draw the partially-reflected ray. Do not draw the partially reflected ray in a ray diagram unless specifically instructed to do so.

 

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