A laptop logon screen can barely be seen, despite adjusting the display's brightness setting. Which of the following display components is defective?

The backlight provides the light source that makes LCD content visible; when it fails or degrades severely, the screen image becomes extremely dim or nearly invisible even though the panel itself is still producing an image. This matches the symptom described - the logon screen can 'barely be seen,' meaning the display circuitry is functional but the illumination source is not. Modern laptops use LED backlights that can fail independently of other display components.

The digitizer is a touch-sensitive layer used in touchscreen devices and has no effect on display brightness or visibility.

The inverter converts DC to AC to power older CCFL-based backlights; while inverter failure produces similar symptoms on legacy laptops, the root cause of dim output is still the backlight assembly itself, and the given correct answer is the backlight.

The polarizer is a filter layer in the LCD stack that affects contrast and viewing angle, but failure would distort or discolor the image rather than simply dim it.