- The Joint Comprehensive Plan of Action (JCPOA; Persian: برنامه جامع اقدام مشترک, romanized: barnāmeye jāme’e eqdāme moshtarak (برجام, BARJAM)), commonly known as the Iran nuclear deal or Iran deal, is an agreement on the Iranian nuclear program reached in Vienna on July 14, 2015, between Iran and the P5+1 (the five permanent members of the United Nations Security Council—China, France, Russia, the United Kingdom, United States—plus Germany) together with the European Union.
- f-number (Wikipedia)
An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system’s focal length by the diameter of the entrance pupil (“clear aperture”). The f-number is also known as the focal ratio, f-ratio, or f-stop, and it is key in determining the depth of field, diffraction, and exposure of a photograph. The f-number is dimensionless and is usually expressed using a lower-case hooked f with the format f/N, where N is the f-number.