Making a sprite visible over a duration?

Hi guys,

Say I want a laser/lightning effect to occur on a platformer. I could have this as a sprite and make it visible, but I'd really like to make the sprite visible over say 0.5 seconds. So it draws the sprite from top to bottom over that time so it actually looks like time has passed when the laser activates.

Or is there a better way to do that sort of thing?

Thanks!

would using tiled background or 9-patch and setting height or width work?