The sky appears dark to passengers flying at very high altitudes mainly because:
The sky appears dark to passengers flying at very high altitudes mainly because:
Options
The sky appears dark to passengers flying at very high altitudes mainly because scattering of light is not prominent or enough at such heights due to the extremely thin atmosphere.
Marking Scheme
- 1Identification of correct option (A) (1 mark)
Hint
Think about what causes the sky to look blue from the ground. It requires particles to scatter sunlight. At very high altitudes, what happens to the density of these particles?
Quick Oral Answer
The sky appears dark at high altitudes because the atmosphere is very thin, meaning there are very few particles to scatter sunlight. Without scattering, no light reaches our eyes from the surrounding sky, making it look black.
Analysis & Explanation
At very high altitudes, the concentration of air molecules, dust, and other fine particles is extremely low (the atmosphere is very thin). Since scattering of light requires the presence of these particles to interact with sunlight, the lack of sufficient particles means that light is not scattered in different directions. Consequently, no scattered light enters the eyes of the passengers, and the sky appears dark or black.
- Option A is correct because the lack of scattering particles at high altitudes prevents the scattering of light.
- Option B is incorrect because while the atmosphere is extremely thin, saying there is absolutely 'no atmosphere' at typical commercial or high-altitude flight levels is technically inaccurate.
- Option C is incorrect because the size of air molecules being smaller than the wavelength of visible light is the reason for the blue colour of the sky at lower altitudes (Rayleigh scattering), not the reason for darkness at high altitudes.
- Option D is incorrect because light is not preferentially scattered towards the Earth to make the sky look dark at high altitudes.
Common Mistakes
- 1Students often confuse the thin atmosphere with a complete vacuum (Option B).
- 2Some students select Option C thinking it relates to Rayleigh's scattering law without connecting it to the physical density of the atmosphere at high altitudes.
Interesting Facts
Astronauts in space see the sky as completely black and can see stars clearly even during the daytime because there is no atmosphere to scatter sunlight and create a bright background.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2020?
This question carries 1 mark in the CBSE Class 10 Science 2020 examination.
Which chapter does this question come from in Science?
This question is from the chapter "The Human Eye and the Colourful World" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Scattering of Light" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2020 paper?
This is a MCQ question from Section A in the CBSE Class 10 Science 2020 paper.