OK. I see what's going on here. To answer all of these, you have to know two basic things about the electric field. (THAT's the whole purpose of the question ... to help you determine whether you're clear on these two things, or need to go over them.)
Thing #1). The larger the charge is, the stronger the field is around it, and a stronger field is indicated with more lines.
Thing #2). The direction of the lines is the direction of the force on a tiny positive charge in the field. If the charge in the middle is positive, then another tiny positive charge gets pushed away from it ... the lines point OUT. If the charge in the middle is negative, then a tiny positive charge gets attracted to it ... the lines point IN. _________________________
drawing a). lines point in, charge in the middle is negative thickest set of lines . . . biggest negative charge
drawing b). lines point out, charge in the middle is positive thicker than average lines . . . biggest positive charge
drawing c). lines point in, charge in the middle is negative thin lines . . . negative charge in the middle is kind of small
drawing d). lines point out, charge in the middle is positive thin lines . . . positive charge in the middle is kind of small ___________________________
I just looked through the charges, to see what they gave us for positive, negative, big ones, little ones, etc. BE CAREFUL when you decide which charge to put in the middle. Don't just look at the beginning numbers ... be sure and consider the exponents too.
One simple explanation is that planets move, while stars remained fixed in the sky. You can observe a planet's orbit, but a star will stay in the same position.
The phenomenon which is responsible for this effect is called diffraction.
Diffraction is the ability of a wave to propagate when it meets an obstacle or a slit. When the wave encounters the obstacle or the slit, it 'bends' around it and it continues propagate beyond it. A classical example of this phenomenon is when a sound wave propagates through a wall where there is a small aperture (as in the example of this problem)
