Tag: science & technology

Solar cells (photovoltaic cells) are typically made from silicon, a semiconductor material. When photons from sunlight strike silicon atoms, they dislodge electrons, creating an electric current. Silicon's semiconductor properties make it ideal for converting light to electricity.

A solar cell directly converts solar energy (light/photons) into electrical energy through the photovoltaic effect. When photons strike the semiconductor material (usually silicon), they excite electrons, generating a flow of electric current. This is not a thermal conversion process.

Enrico Fermi led the team that achieved the first controlled, self-sustaining nuclear chain reaction on December 2, 1942, at the University of Chicago (Chicago Pile-1). While Otto Hahn discovered nuclear fission, Fermi was the first to successfully harness it in a controlled reactor.

The sun's energy comes from nuclear fusion, where hydrogen nuclei combine to form helium in its core. This process releases enormous energy according to E=mc². Fusion requires extremely high temperatures and pressures (15 million °C in the sun's core), unlike fission which splits heavy atoms.

India's first nuclear test, codenamed 'Operation Smiling Buddha,' was conducted on May 18, 1974, at Pokhran in Rajasthan. This made India the sixth nation to detonate a nuclear device. The test was carried out under Prime Minister Indira Gandhi's leadership.

Motorola was the first company to launch a mobile phone. On April 3, 1973, Motorola engineer Martin Cooper made the first public handheld mobile phone call using the DynaTAC prototype. The phone took 10 hours to charge and offered 30 minutes of talk time. Commercial versions were launched in 1983.

Martin Cooper is widely credited as the inventor of the first handheld mobile phone. While working at Motorola, he led the team that developed the DynaTAC phone. He made the first public mobile phone call on April 3, 1973, to Joel Engel at Bell Labs - his rival in the race to develop mobile technology.

Early mobile phones were large, heavy, and rectangular, earning them the nickname 'brick phones' or simply 'bricks'. The Motorola DynaTAC 8000X, for example, weighed 2.5 pounds and was about the size of a brick. The term has persisted as slang for any large, outdated phone.

The 1984 film 'Sixteen Candles' is believed to be the first movie to feature a mobile phone. The character Jake Ryan uses a Motorola DynaTAC phone in the film. This was years before mobile phones became commonplace, making it a notable early appearance in popular culture.

Philippe Kahn invented the first camera phone in 1997. He created a prototype that could instantly share photos by connecting a digital camera to his mobile phone. The first photo was of his daughter Sophie's birth. This innovation paved the way for the camera phones that would become ubiquitous.