UPSC CSE Prelims
Question 94
A layer in the Earth's atmosphere called Ionosphere facilitates radio communication. Why ?
- The presence of ozone causes the reflection of radio waves to Earth.
- Radio waves have a very long wavelength.
Which of the statements given above is/are correct ?
View correct answer and explanation
Correct answer: D
Correct Option: D
Explanation: The ionosphere refracts/reflects certain radio frequencies because solar radiation ionises gases and creates free electrons; ozone and wavelength alone do not explain it.
Statement / Item-wise Analysis:
1: Incorrect - Incorrect: the reflecting/refracting effect comes from ionised plasma, not atmospheric ozone.
2: Incorrect - Incorrect as a sufficient cause: radio wavelengths vary widely and the ionosphere’s electron density is what enables skywave propagation.
Option-wise Analysis:
A: Incorrect - includes unsupported item 1.
B: Incorrect - includes unsupported item 2.
C: Incorrect - includes unsupported items 1, 2.
D: Correct - correctly excludes all the listed statements.
Review Note: Question omits the actual mechanism (free electrons in ionised layers); the correct answer is “neither.”