In optics there are critical angles. This is an angle where there will be no more refraction through a surface, all the light will be reflected. As shown in the figure, as soon as the light hits the critical angle, no light escapes the medium. This is what is happening it the glass prism. 

Two diverging lenses were used.  The one closest to the laser had a focal length of 50 mm. This lens  will expand after its focal point. The second lens had a focal length of 50 mm to culminate the light into one expanded beam as shown in the figure.

When building a basic telescope, two lenses were used. Their focal lengths can be added to find the distance between the lenses. The focal lengths will meet at one point. This will allow the eyepiece to take the image from the objective which will be inverted and make it look upright and magnified.