Question

Planets do not twinkle because:

• A. They are nearer to Earth and hence we receive a greater amount of light
• B. They are very far away resulting in decreased intensity of light
• C. They emit light of constant intensity
• D. Their distance from Earth does not change with time

Hint:

Think about the difference between a point source and an extended source of light passing through a turbulent atmosphere.

Answer 1

The Correct Option is A

Step 1: Recall why stars twinkle.
Stars are extremely far away and act as point sources of light. Their light passes through many constantly moving, turbulent layers of Earth's atmosphere, causing rapid changes in brightness called twinkling or scintillation.
Step 2: Compare planets with stars.
Planets are much closer to Earth than stars, so instead of appearing as a single point of light, a planet appears as a tiny extended disc made up of many close together points of light.
Step 3: Explain the averaging effect.
The twinkling caused by atmospheric turbulence affects each point on this disc slightly differently at any instant, and these small variations average out over the whole disc, so the total brightness reaching the eye stays fairly steady.
Step 4: Connect to the option.
This steadiness is possible because planets are nearer to Earth, which is what allows them to be seen as a broader disc receiving and sending back a comparatively larger, steadier amount of light.
Step 5: Rule out other options.
Planets are not far away compared to stars, and intensity is not decreased due to distance here. Planets do not emit their own light at all, they only reflect sunlight. Planetary distance from Earth does change slightly during orbit, and this is not the reason twinkling is absent anyway.
Final Answer: A) They are nearer to Earth and hence we receive a greater amount of light.