Solar Radiation and Energy

Infrared radiation from sunlight is primarily responsible for the sensation of heat because it's absorbed by our skin and converted to thermal energy. Visible light provides illumination, and ultraviolet radiation causes sunburn but doesn't primarily feel hot.

Ultraviolet (UV) radiation from the sun is harmful because it damages DNA and causes skin cancer, sunburn, and premature aging. Visible light and infrared are not harmful at normal exposure levels, and radio waves from the sun are weak.

Ultraviolet (UV) radiation from the sun penetrates the skin and damages DNA in skin cells. Over time, this accumulated damage can lead to mutations that cause skin cancer, including melanoma. UV radiation is classified as a carcinogen by health organizations.

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.

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.

Stars generate energy through thermonuclear fusion reactions, converting hydrogen into helium and releasing energy according to E=mc². Solar and electric power are just ways of capturing or using existing stellar energy.

The Earth receives solar energy from the Sun, which is the star at the center of our solar system. The Moon only reflects sunlight, while Venus and Mercury are planets that do not produce their own light. The term 'solar' literally means 'of the Sun'.

Stars generate energy through nuclear fusion in their cores, where extreme temperatures and pressures enable hydrogen nuclei to combine into helium nuclei. This process releases energy because the total mass of the products is slightly less than the mass of the reactants - this mass difference is converted to energy. Nuclear fission involves splitting heavy nuclei, which doesn't occur in normal stellar cores.

Cadmium telluride (CdTe) is a crystalline compound formed from cadmium and tellurium. It is used as an infrared optical window and a solar cell material. It is usually sandwiched with cadmium sulphide to form a p-n junction photovoltaic solar cell. Typically, CdTe cells use a n-i-p structure.

The sun's energy is produced by nuclear fusion - hydrogen nuclei combine to form helium, releasing enormous energy. This occurs in the sun's core under extreme temperature and pressure. Chemical reactions and combustion are surface processes; nuclear fission is not the sun's energy source.

Carbon dioxide is transparent to incoming shortwave solar radiation but absorbs and re-emits longwave terrestrial (infrared) radiation. This selective absorption is the fundamental mechanism of the greenhouse effect, trapping heat in the atmosphere while allowing sunlight to reach Earth's surface. Nitrogen and oxygen, which comprise most of the atmosphere, do not have this property.

The Fraunhofer D-lines are dark absorption lines in the solar spectrum caused by sodium in the sun's outer atmosphere (photosphere/chromosphere). These cooler layers absorb specific wavelengths, creating dark lines in the otherwise continuous spectrum.

The Sun's energy travels through the vacuum of space by radiation (electromagnetic waves). Conduction requires a medium, convection requires fluid motion with gravity, and only radiation can travel through empty space. This is how we receive solar energy.

In the vacuum of space between Sun and Moon, there is no medium for conduction or convection - both require matter. Heat transfer can only occur through radiation (electromagnetic waves), which needs no medium.