The relationship between glScalef() and light intensity

OpenGL OpenGL: Advanced Coding
1

I used to call glScalef(…) to zoom in/out the scene. But I found that the light brightness will be reduced if I zoom in the scene by increase the glScale(…) parameters. And I am sure that other gl parameters are unchanged while glScale paramters increasing.
Can you tell me the relationship between brightness and scale? Thanks.

2

the normals are also scaled.
this is answered in the faq www.opengl.org rightside of page

3

Use glEnable(GL_NORMALIZE);