If it’s normal dividend (lesser than 5%), market factors in the dividends and this is when F&O generally trade at discount to spot price.
If it is an extraordinary dividend (greater than 5%), in such cases the exchange has Adjustment Formula, through which they adjust Price, Strike Price, Lot Size of F&O such a way that that the value of the position of the market participants, on the cum and ex-dates for the corporate action, shall continue to remain the same as far as possible. There was recent example of REC which was explained here: Adjustment of F&O contracts in REC Limited