Question

Explain with reason:-
(A) Twinkling of stars.
(B) Advanced sunrise and delayed sunset.
(C) Blue colour of sky.
(D) Reddish colour of sky during sunrise and sunset.

Answer 1

Hint:Refraction is phenomena of changing properties of waves when it passes through one substance. Refraction of light changes the direction of ray of light when it propagates from one medium to another medium. These all phenomena occur due to refraction of light in different ways.

Complete step by step answer:
(A)Twinkling of stars:This phenomenon appears to us because of continuous change in atmospheric density of layers of atmosphere due to sunlight. As atmosphere density increases or decreases in any of the atmospheric layers it causes change in intensity of light.
(B)Advanced sunrise and delayed sunset: Before sunrise, sun’s rays pass through denser air to less dense air, causing rays to refract and appear to be coming from above the horizon whereas sun is below the horizon at this time. It looks like rays are coming straight from the sun and sunrise has happened. It is the reason behind the advance sunrise.
After sunset, the sun goes below the horizon. Sun’s rays pass through denser air to less dense air, it causes rays to refract and appear to be coming from above the horizon whereas the sun is below the horizon at this time. It looks like rays are coming straight from the sun and sunset has not happened. This is the reason for the delayed sunset.
(C) Blue colour of sky: At the time between sunrise and sunset sun is closer to the position of the viewer than earlier. As sunlight consists of seven colors out of which blue light has the shortest wavelength, due to this blue light scatters more and the sky looks blue to us.
(D) Reddish colour of sky during sunrise and sunset: At the time of sunrise and sunset sun is not closer to the position of the viewer than at other times. As sunlight consists of seven colors out of which red light has the highest wavelength, due to this red light scatters less and the sky looks reddish to us at a time of sunrise and sunset.

Note:Reason behind formation of rainbows in the sky during rainy days is also refraction. During rainy days water droplets are available in the atmosphere due to it sunlight goes through multiple refractions which causes a split of sunlight into seven colors.