Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. However, when the absorbed electromagnetic radiation is intense, it is possible for one electron to absorb two photons; this two-photon absorption can lead to emission of radiation having a shorter wavelength than the absorbed radiation. The emitted radiation may also be of the same wavelength as the absorbed radiation, termed "resonance fluorescence".

The most striking examples of fluorescence occur when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, and the emitted light is in the visible region.

Fluorescence has many practical applications, including mineralogy, gemology, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, biological detectors, and, most commonly, fluorescent lamps.

Kate Marie Nash (born 6 July 1987) is an English singer, songwriter and musician. She had a UK number-2 hit "Foundations" in 2007, followed by the platinum-selling UK number-1 album Made of Bricks. She was named Best Female Artist at the 2008 BRIT Awards.

Her second studio album, entitled My Best Friend Is You, was released in the United Kingdom on 19 April 2010 and in the U.S. on 11 May 2010. It spawned her second biggest chart hit to date, the single "Do-Wah-Doo".

Nash is currently signed to The Island Def Jam Motown Ireland Group.

Nash was born on 6 July 1987 in Harrow, London to an English father, Steven Nash, and an Irish mother, Marie (née Walsh). Marie is a nurse in a hospice. Nash learned to play the piano while at at Sandbach School. She was raised as a Roman Catholic and attended St. John Fisher School, Pinner, before moving onto the St Joan of Arc Catholic School, Rickmansworth. She was also taught guitar by Saskia van Berkel and studied Theatre at the BRIT School for Performing Arts and Technology in South London. She auditioned at the Bristol Old Vic Theatre School, but was rejected. Soon afterward, she fell down a flight of stairs, breaking her foot. During her recovery, she was housebound and unable to move, so her mother bought her an electric guitar. Nash used this time to focus on her songwriting: she began to write some new songs, finish old ones and decided that she would book a gig at a local bar ("Trinity") in Harrow to showcase her songs.^{[citation needed]}

Jonathan Stephen Ross, OBE (born 17 November 1960) is an English television and radio presenter, best known for presenting the BBC One chat show Friday Night with Jonathan Ross from 2001 until he left the BBC in 2010. Ross began hosting a new chat show on ITV1 starting 3 September 2011. Ross also hosted his own radio show on BBC Radio 2, and acted as a film critic and presenter of the Film programme. Other regular roles have included being a regular panellist on the comedy sports quiz They Think It's All Over from 1999 to 2006, and presenting the annual British Comedy Awards from 1991 to 2007, and 2009 onwards.

Ross began his television career as a programme researcher, before débuting as a television presenter for The Last Resort with Jonathan Ross on Channel 4 in 1987. Over the next decade he had several radio and television roles, many through his own production company, Channel X. In 1995 he sold his stake in Channel X, and embarked on a career with the BBC. In 1999, Ross took over presenting the Film programme from Barry Norman, and also began presenting his own radio show, while two years later he began hosting Friday Night with Jonathan Ross. For the chat show, Ross won three British Academy of Film and Television Arts (BAFTA) awards for Best Entertainment Performance, in 2004, 2006 and 2007. By 2006 Ross was believed to be the BBC's highest paid star. In 2005, Ross was made an Officer of the Order of the British Empire (OBE) for services to broadcasting. Ross has been involved in controversies throughout his broadcasting career. As a result, in 2008 he wrote a semi-autobiographical work titled Why Do I Say These Things?, detailing some of his life experiences.

David Michael Letterman (born April 12, 1947) is an American television host and comedian. He hosts the late night television talk show, Late Show with David Letterman, broadcast on CBS. Letterman has been a fixture on late night television since the 1982 debut of Late Night with David Letterman on NBC. Letterman recently surpassed friend and mentor Johnny Carson for having the longest late-night hosting career in the United States of America.

Letterman is also a television and film producer. His company Worldwide Pants produces his show as well as its network follow-up The Late Late Show with Craig Ferguson. Worldwide Pants has also produced several prime-time comedies, the most successful of which was Everybody Loves Raymond, currently in syndication.

In 1996, David Letterman was ranked #45 on TV Guide's 50 Greatest TV Stars of All Time.

Letterman was born in Indianapolis, Indiana. His father, Harry Joseph Letterman (April 1915 – February 1973), was a florist of British descent; his mother Dorothy Letterman (née Hofert, now Dorothy Mengering), a Presbyterian church secretary of German descent, is an occasional figure on the show, usually at holidays and birthdays.