Prelims 2011 · archive
EasyA layer in the Earth’s atmosphere called Ionosphere facilitates radio communication. Why?
- 1.The presence of ozone causes the reflection of radio waves to Earth.
- 2.Radio waves have a very long wavelength.
Which of the statements given above is/are correct?
Answer & explanation
Answer: (d) Neither 1 nor 2
The ionosphere helps radio communication because it contains electrically charged particles (ions) that reflect radio waves back to Earth. Ozone is not the cause: it is concentrated in the stratosphere, well below the ionosphere. Radio wavelength is not the reason the layer works either. So neither statement is correct.
- ✗ 1. The ozone layer lies in the stratosphere, which extends up to about 50 km, and it absorbs ultraviolet radiation. The ionosphere lies at about 80–400 km and is named for its ions, not for ozone. Ozone plays no part in reflecting radio waves.
- ✗ 2. The ionosphere reflects radio waves because it is a layer of electrically charged particles. The wavelength of radio waves is not what makes this layer useful for communication, so the statement does not explain it.
- ✓ (d) Neither statement gives the real reason, which is the presence of ions in the layer between about 80 and 400 km.
Remember · The ionosphere (about 80–400 km) is a layer of ions that reflects radio waves back to Earth. Ozone sits in the stratosphere and absorbs ultraviolet radiation.
📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 7 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 7 (practise this chapter)
Sources
- NCERT Class 11 · Fundamentals of Physical Geography, Chapter 7 “It contains electrically charged particles known as ions, and hence, it is known as ionosphere. Radio waves transmitted from the earth are reflected back to the earth by this layer.”
- NCERT Class 11 · Fundamentals of Physical Geography, Chapter 7 “One important feature of the stratosphere is that it contains the ozone layer. This layer absorbs ultra-violet radiation and shields life on the earth from intense, harmful form of energy.”
Question: UPSC Civil Services (Preliminary) 2011, General Studies paper. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·