Question

Which phenomenon listed in the options below is responsible for the twinkling of stars?

• A. Atmospheric reflection
• B. Atmospheric refraction
• C. Dispersion
• D. Total internal reflection

Hint:

Remember that light bends (refracts) when it passes from one medium to another with a different density, like from space to air, or between different layers of air. This is the key principle behind phenomena like twinkling stars and mirages.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The question asks for the physical phenomenon that causes stars to appear to twinkle when viewed from Earth.
Step 2: Detailed Explanation:
- Starlight travels from the vacuum of space into the Earth's atmosphere. The atmosphere is not uniform; it consists of many layers of air with varying temperatures, densities, and pressures.
- Because of these variations, the refractive index of the air is constantly changing and fluctuating at different points along the light's path. - As the starlight passes through these turbulent layers, it is bent, or refracted, multiple times in random directions.
- This continuous and random bending of light causes the apparent position of the star to shift slightly and the amount of light reaching the observer's eye to vary from moment to moment.
- This fluctuation in brightness and apparent position is what we perceive as the twinkling of stars. This phenomenon is correctly termed atmospheric refraction.
- Planets, being much closer to Earth, appear as extended sources of light (tiny discs) rather than point sources. The light from different points on the planet's disc is also refracted, but the fluctuations tend to average out, which is why planets generally do not appear to twinkle.
Step 3: Final Answer:
The twinkling of stars is caused by atmospheric refraction.