Here's a couple different solutions you can try to see what's causing the problem:
* If you are able to adjust the screen brightness using the function keys on your keyboard (Fn + F6), try to increase the brightness
* If the previous solution doesn't work, try shining a flashlight on the screen. If you can see an image only when using a flashlight, this indicates a backlight failure
* If you have an HDMI monitor you can connect to the laptop, try connecting it to see if the external monitor works with the laptop