https://padlet.com/acanto1611/3yquakr9bykf A piece of it on a vast universe en-us 2018-09-14 17:00:38 UTC 2025-12-06 23:44:49 UTC hello@padlet.com https://padlet-assets.s3.amazonaws.com/icons/Bigthunderstorm.png acanto1611 https://padlet.com/acanto1611/3yquakr9bykf/wish/281428609 Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to visible light, which is the visible spectrum that is visible to the human eye and is responsible for the sense of sight.^[1] Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), or 4.00 × 10⁻⁷ to 7.00 × 10⁻⁷ m, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths).^[2][3] This wavelength means a frequency range of roughly 430–750 terahertz (THz).]]> 2018-09-14 17:14:50 UTC https://padlet.com/acanto1611/3yquakr9bykf/wish/281428609 acanto1611 https://padlet.com/acanto1611/3yquakr9bykf/wish/281431970 The speed of light in a vacuum is defined to be exactly 299,792,458 m/s (approx. 186,282 miles per second). The fixed value of the speed of light in SI units results from the fact that the metre is now defined in terms of the speed of light. All forms of electromagnetic radiation move at exactly this same speed in vacuum.]]> 2018-09-14 17:20:55 UTC https://padlet.com/acanto1611/3yquakr9bykf/wish/281431970 acanto1611 https://padlet.com/acanto1611/3yquakr9bykf/wish/281432570 There are many sources of light. A body at a given temperature emits a characteristic spectrum of black-body radiation. A simple thermal source is sunlight, the radiation emitted by the chromosphere of the Sun at around 6,000 kelvins (5,730 degrees Celsius; 10,340 degrees Fahrenheit) peaks in the visible region of the electromagnetic spectrum when plotted in wavelength units^[18] and roughly 44% of sunlight energy that reaches the ground is visible.^[19] Another example is incandescent light bulbs, which emit only around 10% of their energy as visible light and the remainder as infrared. A common thermal light source in history is the glowing solid particles in flames, but these also emit most of their radiation in the infrared, and only a fraction in the visible spectrum.]]> 2018-09-14 17:22:03 UTC https://padlet.com/acanto1611/3yquakr9bykf/wish/281432570 acanto1611 https://padlet.com/acanto1611/3yquakr9bykf/wish/281435178 2018-09-14 17:27:01 UTC https://padlet.com/acanto1611/3yquakr9bykf/wish/281435178