What Does a CCD Pixel Measure?

[blue_leaf77]

I have a got a problem regarding what a CCD pixel actually measures. Suppose I have a pixel of area dx dy. A plane wave of intensity I₀ is impinging on the pixel making an angle α with the normal of pixel surface. The flux going into the pixel would be F = I₀ dx dy cos(α). My question what is the pixel directly sensitive to, is it F or I₀ cos(α)?

 

[jedishrfu]

The I0 cos(a) is the intensity per unit area whereas your actual area is dx by dy. Right?

 

[blue_leaf77]

You can say so, but strictly speaking I₀ cos(a) is the projection of intensity vector (or Poynting vector) to the normal of the pixel surface. The actual area is dx dy.