In particular, the photon model accounted for the frequency dependence of light's energy, and explained the ability of matter and radiation to be in thermal equilibrium.he energy of a system that emits a photon is decreased by the energy of the photon as measured in the rest frame of the emitting system, which may result in a reduction in mass in the amount. Similarly, the mass of a system that absorbs a photon is increased by a corresponding amount.
Responding to the changes, the Finnish company started churning out both sophisticated multimedia handsets as well as low-end devices. The year 2001 saw the company launching the Nokia 7650, its first phone to feature a built-in camera. It was also the first to sport a full color display.
Nokia's first fully portable mobile phone (after the Mobira Senator car phone of 1982) was the Mobira Cityman 900 in 1987. Nokia assisted in the development of the GSM mobile standard in the 1980s, and developed the first GSM network with Siemens (predecessor of Nokia Siemens Network).