Answer:
The force exerted on the cardboard by the light is

Step-by-step explanation:
It is given that,
Area of the cardboard,

Intensity of absorbance,

Radiation pressure in case of absorption is given by :
...........(1)
c is the speed of light
The relation between force and pressure is given by :
.......(2)
From equation (1) and (2):



So, the force exerted on the cardboard by the light is
. Hence, this is the required solution.