Pure expectation theory discount, expected, interest, anybody, shorter

nixie24

As per one of the sentence of the subjected theory "If short term rates are expected to rise in the future, interest rate yields on longer maturities will be higher than those on shorter maturities"

Could anybody help me in understanding this better? If rate rises than the PV of the bond will be at discount, how come interest rate yields on longer maturities will be high?

Thanks in advance!