Once through the lens, the ray should pass through the principal focus. Draw a ray which passes from the object through the centre of the lens. Some ray diagrams may also show a third ray.

Once through the lens, the ray should pass through the principal focus. Draw a ray which passes from the object through the centre of the lens. Some ray diagrams may also show a third ray.

Technically, the glasses have a distance sensor embedded into the front of the frame and continually adjust the focus of the lenses. An 8 gram, 110 mAh battery powers the prototype for roughly 6 ...