Question

3.Light with an average flux of 20 W/cm2 falls on anon-reflecting surface at normal incidence havingsurface area 20 cm2. The energy received by thesurface during time span of 1 minute is:(1) 12 x 103 J(2) 24 x 103 J(3) 48 x 103J (4)10 X 103 J​

Answer 1

Explanation:

The intensity of the light incident is given by:

I=

At

E

Here, I=20W/cm

2

, Area A=20cm

2

, time t=1min=1×60sec=60sec

∴20=

20×60

E

⇒E=20×20×60

E=24×10^3 J

Option 24×10^3 Jis correct