Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics. Historically, the ray-based model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that light waves were in fact electromagnetic radiation.
A game is structured form of play, usually undertaken for enjoyment and sometimes used as an educational tool. Games are distinct from work, which is usually carried out for remuneration, and from art, which is more often an expression of aesthetic or ideological elements. However, the distinction is not clear-cut, and many games are also considered to be work (such as professional players of spectator sports or games) or art (such as jigsaw puzzles or games involving an artistic layout such as Mahjong, solitaire, or some video games).
Games (遊戲 - 基) is an album by the Cantopop singer Leo Ku, released on November 28, 2003. The album is based on the theme of video games and was recorded in 2003 after Ku's two-year break from singing Cantopop. His current manager, Paco Wong, persuaded Ku to come back to Hong Kong's Cantopop scene. The songs 必殺技 ("Fatal Trick") and 任天堂流淚 ("Let Heaven Shed its Tears") won Ku numerous awards.