Assuming the velocity of EM waves reaching an antenna as

Assuming the velocity of EM waves reaching an antenna as 3 × 10⁸ m/sec the length of a half wave dipole antenna required to receive a 5 MHz radio signal is—

We have effective length as l_effe =	1
We have effective length as l_effe =	2

where l is the actual length of uniform current wave for λ/2 antenna (half wave dipole)

λ	=	3 × 10⁸	= 30 m; l = l_effe × 2 = 60
2	=	5 × 2 × 10⁸	= 30 m; l = l_effe × 2 = 60