We know that evaporation is a surface phenomenon. If the surface area is increased, the rate of evaporation increases. For example, while putting clothes for drying up we spread them out.
Well we know that evaporation happens due to many properties like humidity, wind speed and even surface area. When there more surface area then the evaporation process will also be more. 

Example : 
When we drink tea in the cup the tea will be hot for a longer period of time because the surface area of the cup is very less. Again when we drink the tea in the saucer then the tea doesn't stay hot for longer time it because the surface area of the saucer is more when compared that of cup hence the evaporation process is more here. Hence proved that evaporation depends on the surface area.