Question

Assertion: The twinkling of stars is due to the fact that refractive index of the earth’s atmosphere fluctuates.
Reason: When light propagates from one medium to another its direction of propagation does not change.

Answer 1

$\: \: \: \: \: \: \: \: \: \: \: \: \bigstar\large \purple{ \underline { \pmb{ \sf question.... }}}$

Assertion: The twinkling of stars is due to the fact that refractive index of the earth’s atmosphere fluctuates.

Reason: When light propagates from one medium to another its direction of propagation does not change.

Identity the correct option about these sentences:-

• Both A and R are true and R is correct explanation of A
• Both A and R are true But R is not the correct explanation of A
• A is true R is false
• A is false R is true.

$\: \: \: \: \: \: \: \: \: \: \: \: \bigstar\large \purple{ \underline { \pmb{ \sf answer ....}}}$

$\sf \pink{(c) \: a \: is \: true \: but \: r \: is \: false}$

$\: \: \: \: \: \: \: \: \: \: \: \: \bigstar\large \purple{ \underline { \pmb{ \sf explanation ....}}}$

The phenomenon of Twinkling of stars occurs due to the atmospheric refraction. This occurs due to varying / fluctuating refractive indices of the layers of atmosphere

$\sf \green{ \therefore \: assertion \: is \: correct \: \checkmark }$

when light propagated through these different atmosphere refraction it bends towards the normal and hence, it's direction changes.

$\sf \red{ \therefore \: reason \: is \: wrong \: ✘ }$

Answer 2

Assertion is true but reason is false.

Explanation:

• Earth's atmosphere has different layers and all layers have different temperature.
• This is a reason why density of atmosphere is variable. It is not constant throughout the medium.
• The portion or layer of atmosphere that is cool has higher refractive index than warm layers.
• This difference in refractive index causes atmospheric refraction.
• Sunlight passes through the atmosphere which has multiple layers of different refractive index and refraction takes place.
• Atmosphere is denser closer to the surface of Earth than it is higher up.

Twinkling of stars is also a cause of atmospheric refraction because refractive index is not constant, rather it fluctuates for the earth's atmosphere.

Due to continuous refraction, direction of light propagation changes when travelling from one medium to another.