DISPERSION AND ATMOSSPHERIC REFRACTION Flashcards
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how does a rainbow occur?
A Rainbow is a natural spectrum appearing in the sky after a rain shower it is caused by the dispersion of sunlight by tiny water droplets in the atmosphere. The rainbow is formed in the opposite direction to that of the sun. The water droplets act like a tiny prism . they refract and disperse the incident sunlight then reflect it internally and finally reflect it when it comes out of the raindrop due to the dispersion of light and reflection, different colour reaches the observer’s eye.
WHY DOES THE AIR JUST ABOVE THE FIRE fluctuate?
The hotter air is lighter (less dense) than the cooler air above it and has a refractive index slightly less than that of the cooler air. Since the physical conditions of the refracting medium (air) are not stationary, the apparent position of the object, as seen through the hot air, fluctuates.
WHY DO THE STAR TWINKLE?
the twinkling of stars is due to the atmospheric refraction of starlight. The starlight before entering the atmosphere undergoes refraction continuously before entering the earth’s surface. Atmospheric refraction occurs in a medium gradually changing its refractive index since the atmospheric refraction bends the starlight toward the normal the apparent position is different from its actual position this apparent position is not stationary but keeps changing slightly since the physical condition of the earth’s atmosphere is not stationary.
why planet don’t twinkle?
the planet are much closer to the earth and thus are the extented source of light .If we consider planet as a collection of large number of point sized sources of light the total varition of large amount of light entering our eye from all the indivuals point size source average out zero there by nullifying the twikling effect
explain the advanced sun rise and delayed sun set
Sunrise and Sunset is actuaaly the crossing of horizon by the sun . The advanced sunrise and delayed sunset id due to the atmospheric refraction . The difference between the actual sunrise and apprant sunrise is 2 minutes likewise the difference between actual sun set and apprant sunset is 2 minutes . The fllatering of sun’s disc is also due to this phenomena
what is tyndall effect ?
Explain its instances
when the beam of light strikes the fine particles of dust tiny water molecules and molecules present in air the path of light becomes visible . The light reaches us after bieng reflected diffusely by thses particles . This phenomena of scattering of light by clloidal particles gives rise to tyndall effect
THIS INSTANCE OBSERVATION CAN BEEN SEEN IN
1)The fog
2)light passes through canopy in forest
3) blue colour of sky
4) light passing through milk
Explain why the colour of the scatterd light particles depends on the size of the scattering paritcles-
fine particle scatter mainly in blue light while the particle of larger size scatter in longer wavelenght . If the size of the
scatterd particles are large enough then the color may even appear white.
what causes the blue colour of sky?
the molecules of air and other fine particles present in the atmosphere has a size smaller than that of wavelenght of visible light . This is more effective in scattering the light of shorter wavelenght at the blue end than the longer wavelenght at the red end . The red light has a wavelenght of about 1.8 times greater than blue light . Thus when the sunlight passes through the atmosphere the air particles sctter the blue mostly the red light . The scatterd blue light enter our eye
why does the sky appear dark to the passengers?
the sky appear dark to the passengers flying at very high altitudes as scattering is not prominent at such height
