Comment on ‘The paradoxical zero reflection at zero energy’

We point out that the anomalous threshold effect in one dimension occurs when the reflection probability at zero energy R(0) has some other value than unity, rather than R ( 0 ) = 0 or R ( 0 ) ≪ 1 as implied by Ahmed et al in their paper entitled ‘The paradoxical zero reflection at zero energy’ (2017 Eur. J. Phys. 38 025401).