A 620 lines/mm diffraction grating is in an empty aquarium tank. The index of refraction of the glass walls is nglass= 1.50. A helium-neon laser ( ? = 633 nm) is outside the aquarium. The laser beam passes through the glass wall and illuminates the diffraction grating. What is the first-order diffraction angle of the laser beam? What is the first-order diffraction angle of the laser beam after the aquarium is filled with water ( nwater= 1.33)?

Which explanation describes the forces involved for a person to walk down the sidewalk? a. the person's feet push backward on the sidewalk; the sidewalk pushes backward on the person. b. the person's feet push forward on the sidewalk; the sidewalk does not push on the person. c. the person's feet push backward on the sidewalk; the sidewalk pushes forward on the person. d. the person's feet push forward on the sidewalk; the sidewalk pushes forward on the person.

In positive numbers less than 1, the zeros between the decimal point and a non-zero number are blank significant

The coefficient of friction is a number that represents the resistance to sliding between two in contact with one another.