Film speed is used in the exposure equations to find the appropriate exposure parameters. Four variables are available to the photographer to obtain the desired effect: lighting, film speed, f-number (aperture size), and shutter speed (exposure time). The equation may be expressed as ratios, or, by taking the logarithm (base 2) of both sides, by addition, using the APEX system, in which every increment of 1 is a doubling of exposure; this increment is commonly known as a "stop". The effective f-number is proportional to the ratio between the lens focal length and aperture diameter, the diameter itself being proportional to the square root of the aperture area. Thus, a lens set to f/1.4 allows twice as much light to strike the focal plane as a lens set to f/2. Therefore, each f-number factor of the square root of two (approximately 1.4) is also a stop, so lenses are typically marked in that progression: f/1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, etc.
What is used to discover the right exposure parameters?
Film speed

Over the years, AC has spawned subgenres including "hot AC", "soft AC" (also known as "lite AC"), "urban AC", "rhythmic AC", and "Christian AC" (a softer type of contemporary Christian music). Some stations play only "hot AC", "soft AC", or only one of the variety of subgenres. Therefore, it is not usually considered a specific genre of music; it is merely an assemblage of selected tracks from musicians of many different genres.
Along with hot, soft, urban and Christian AC, what is another prominent time of adult contemporary music?
rhythmic AC

The same happens with Arabic loanwords. Thus, Catalan alfàbia "large earthenware jar" and rajola "tile", of Arabic origin, contrast with Spanish tinaja and teja, of Latin origin; whereas Catalan oli "oil" and oliva "olive", of Latin origin, contrast with Spanish aceite and aceituna. However, the Arabic element in Spanish is generally much more prevalent.
What is the origin of the Spanish word teja?
Latin origin