A beam of light having wavelength 5000A is incident on a plane metallic surface.The intensity of the incident beam of light is 40watt and its cross sectional area is 2mm^2.What will be pressure exerted by radiation on metallic surface if 50% of it is reflected back by metallic surface.

Question

samigupta8 · Answer

@ganeshie8

ganeshie8 · Answer

For total absorption :
```
Radiation pressure = Intensity / c
```

For total reflection : 
```
Radiation pressure = 2 * Intensity / c
```

ganeshie8 · Answer

Since the radiation is 50% reflected back and 50% absorbed, the pressure must be something between the above two values.

ganeshie8 · Answer

something between 1/15 and 2/15 : http://www.wolframalpha.com/input/?i=%2840%2F%282*10^%28-6%29%29%29+%2F+%283*10^8%29

samigupta8 · Answer

Hey why did you divide it by cross sectional area of the beam?
The formula is just 2I/c(r) + I/c(a)

ganeshie8 · Answer

Intensity = power/area

samigupta8 · Answer

The use of wavelength then?