AIIMS 2019 Physics Ionospheric Reflection Assertion Reason Question

Option B is correct because the assertion about ionospheric reflection is true; however, the reason provided is not a correct explanation. In ionospheric reflection, radio waves can reflect off the ionosphere without a phase change, similar to total internal reflection, but the reason incorrectly conflates the conditions of reflection in different media. In total internal reflection, the phase change does not occur when reflecting from a rarer medium to a denser medium, which is not directly applicable to the ionosphere's behavior with radio waves. Other options are not relevant as they do not provide valid assertions or reasons.