-18.A diffraction grating that has a uniform distance of 4.0 x 10-4 cm between slits is being illuminated by monochromatic light (a = 6.0 x 10-2 nm) shining perpendicular to the
grating's surface. A second-order maximum will be observed at what angle from the central
maximum?
a.20°
b. 17°
c.90°
d. 0°

İ think its 17 but i am not sure br

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -