Monochromatic light of wavelength 640 nm640\text{ nm}640 nm from a semiconductor laser is incident normally on a diffraction grating with 3.5×105 lines m−13.5 \times 10^5\text{ lines m}^{-1}3.5×105 lines m−1.
What is the total number of bright spots that can be observed on a screen placed far from the grating?
444
888
999
111111
