A 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/ correct?

The ionosphere facilitates radio communication because it contains a high concentration of free electrons and ions created by solar radiation, such as UV and X-rays, which reflect radio waves back to Earth [4]. Statement 1 is incorrect because the ozone layer is primarily located in the stratosphere (10–50 km), whereas the ionosphere is located much higher (80–400 km) and its reflective properties are due to ionization, not ozone. Statement 2 is incorrect because the ionosphere's ability to reflect radio waves depends on the frequency and angle of the signal, not simply because they have 'very long' wavelengths [1]. In fact, while low and medium frequencies (longer wavelengths) are reflected, high-frequency waves often pass through into space [1]. Since neither statement accurately explains the mechanism, the correct option is 4.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Ionosphere (80 to 400 km) > p. 278
2. [4] https://radiojove.gsfc.nasa.gov/education/materials/iono.htm