Most optical elements (mirrors, lenses) can be characterized by basically one quantity: their focal length. To understand focal length, we need to know something about the focal point. In the image above, note how the light rays, after they pass through the lens, converge on a single point. Below is a schematic drawing of the above situation. The single point to which the light rays are converging is called the focal point.
Tsk is a sound made by quickly releasing the tongue from the top of the mouth to express disapproval or criticism. An example of tsk is the sound a mother would make while shaking her finger at a child who's done something wrong. (a sound) used to express disapproval, genuine or mock sympathy, etc.: a click, or sucking sound, made by touching the tongue to the hard palate and rapidly withdrawing it.
FAK Definition & Examples. FAK stands for Freight All Kinds. Essentially, FAKs were set up to help shippers who ship items at multiple freight classes ship all those shipments at the same class. It was implemented to facilitate an easier pricing and billing communication between the shipper and the carrier.