An optical engineer is testing the light emitted from two different light sources: a liquid crystal display (LCD) screen and a traditional incandescent filament lamp.
A linear polarising filter is placed between the LCD screen and a photodetector. When the filter is rotated, the detected intensity of light varies and drops to zero at a specific orientation.
The same filter is then placed between the incandescent lamp and the photodetector. When the filter is rotated through any angle, the detected intensity remains completely constant.
Which row in the table correctly identifies the polarisation state of the light waves emitted by each source?
Light from LCD screen: Plane-polarised | Light from incandescent lamp: Unpolarised
Light from LCD screen: Unpolarised | Light from incandescent lamp: Plane-polarised
Light from LCD screen: Plane-polarised | Light from incandescent lamp: Plane-polarised
Light from LCD screen: Unpolarised | Light from incandescent lamp: Unpolarised