The incident ray is refracted towards the normal as it enters the glass prism from air. It is then refracted away from the normal at the boundary between glass and air as it leaves the prism.

70) that Algarotti had found that the prisms available in Italy were unsuitable for repeating Newton's experiments ... It is made of flint glass, and confirmatory evidence of its date has been ...

Final Verdict Glass prisms can be found online for a fraction of the price of the Fractals Filters offering, and these remain a great starting point for anyone looking to experiment with abstract ...