AP EAPCET 08-Jul-2022 Shift 2 Paper

Radiation pressure on a totally absorbing (non reflecting) surface is
Pressure=

F

A

=

I

c

...(i)
Where, I= Intensity,c= speed of light it is given that;
F=10−6N,
A=15cm2=15×10−4m2
Time for which radiation falls on surface continuously, t=20‌min
=20×60 s=1200 s
Speed of light, c=3×108m∕ s
From Eq.(i) we have,
I=

F×c

A

⇒I=

10−6×3×108

15×10−4

=2×105W∕m2
=20×104W∕m2