The Doppler effect explains changes in the length of light waves or sound waves as they move toward you or away from you.

VOA: special.2009.04.29

But some take effect quickly. For example,in six months the new law will bar insurance companies from denying coverage to children with pre-existing health conditions.

VOA: special.2010.03.24

Finance ministers of the 24 advanced and developing economies said the funding increase takes effect immediately with the money coming from the agency's 185 member nations.

VOA: standard.2009.04.26

"We don't want to see these reforms take effect two years from now.

VOA: standard.2009.09.25