The figure shows sunlight falling on a white screen after being pass through yellow and cyan filters.
Which colour is 'X'?
Green
The yellow filter will allow only yellow light to pass through it. Yellow is a secondary colour made up of red and green colour light.
The cyan filter will not allow red light to pass through it as cyan is made from blue and green hence it alollows only blue, green and cyan coloured lights to pass. Therefore the colour of light passing through cyan filter i.e. X is green which is observed on the white screen placed at the end in front of cyan filter.