No, noon is not the same as afternoon. Noon is specifically 12:00 midday - and less precisely, the general time period from about 11:00 am to 1:00 pm. Afternoon has no specific time associated with it, but is the period from 12:00 midday to the equally imprecise 'evening' - but which is generally considered to begin around 5:00 or 6:00 pm.