On Mon, 04 May 2009 21:18:12 +0000, The Medway Handyman wrote:

So that confirms that sunlight is stronger or of different wavelength
than internal lights.

Both.


It's far stronger - I have a nominal 250W 'daylight spectrum' bulb and
the sun through the window still casts shadows when it's on.

The sun is also much wider spectrum than any bulb - around 300-2500nm
wavelength at ground level. We can only see 400-700nm(ish). Even top
quality 'daylight spectrum' bulbs don't bother trying to match the
further reaches of Ultraviolet or Infrared - and we can be glad they
don't...