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This framework came in 1975. [8] It emphasized that a curriculum based on the principles laid out in the framework has to be developed on the basis of research. Thus for NCERT, the 1970s was a decade flushed with curriculum research and development activities to narrate the content and process of education to Indian realities.
The original Arago spot experiment was carried out a decade later and was the deciding experiment on the question of whether light is a particle or a wave. It is thus an example of an experimentum crucis. At that time, many favored Isaac Newton's corpuscular theory of light, among them the theoretician Siméon Denis Poisson. [10]
Example 120,000 lux: Brightest sunlight: 111,000 lux: Bright sunlight 109,880 lux: AM 1.5 global solar spectrum sunlight (= 1,000.4 W/m 2) [3] [circular reference] 20,000 lux: Shade illuminated by entire clear blue sky, midday 1,000–2,000 lux: Typical overcast day, midday 400 lux: Sunrise or sunset on a clear day (ambient illumination) <200 lux
Table of comparative luminous flux of several light sources [7] [8] [9] Source Luminous flux (lumens) 37 mW "Superbright" white LED: 0.20 15 mW green laser (532 nm wavelength) 8.4 1 W high-output white LED: 25–120 Kerosene lantern: 100 40 W incandescent lamp at 230 volts: 325 7 W high-output white LED: 450 6 W COB filament LED lamp: 600 18 W ...
A light-minute is 60 light-seconds, and so the average distance between Earth and the Sun is 8.317 light-minutes. The average distance between Pluto and the Sun (34.72 AU [5]) is 4.81 light-hours. [6] Humanity's most distant artificial object, Voyager 1, has an interstellar velocity of 3.57 AU per year, [7] or 29.7 light-minutes per year. [8]
The daily light integral (DLI) is the number of photosynthetically active photons (photons in the PAR range) accumulated in a square meter over the course of a day. It is a function of photosynthetic light intensity and duration (day length) and is usually expressed as moles of light (mol photons) per square meter (m −2) per day (d −1), or: mol·m −2 ·d −1.
3 Rural sky 6.6–7.0 21.3–21.6 the zodiacal light is striking in spring and autumn, and color is still visible; some light pollution evident at the horizon; clouds are illuminated near the horizon, dark overhead; nearer surroundings are vaguely visible; the summer Milky Way still appears complex; M15, M4, M5, and M22 are naked-eye objects
By timing the eclipses of Jupiter's moon Io, Rømer estimated that light would take about 22 minutes to travel a distance equal to the diameter of Earth's orbit around the Sun. [1] Using modern orbits, this would imply a speed of light of 226,663 kilometres per second, [2] 24.4% lower than the true value of 299,792 km/s. [3]