No, the answer is right. When I put in the 0.4m as R (or 0.16 as R^2) I get correctly - the E1 screen illumination is two times better than E2. Looks like there is a mistake in my own equations, but I can't find where, as it looks like that it must be like that!
Hello everyone, I was reading a physics book and found an exercise. This time I faced with a really strange one! I can't find out what I am doing wrong! I am really good at physics and math, but sometimes I fail as many people do... :smile:
The answer in the book says ~0.4m, but I am unable to...