The $(\mathrm{C}-\mathrm{H})$ bond length order in hydrocarbons in which the hybridisation of carbon is ${\mathrm{sp}}^3$ or ${\mathrm{sp}}^2$ or $\mathrm{sp}$

The bond length in hydrocarbon when the adjacent carbon has different hybridisation is in order.

Hydrocarbon:    Ethane      Ethene       Ethyne
Bond length $1.09A°>1.076A°>1.06A°$

$s{p}^3-s>s{p}^2-s>s{p}^{ }-s$