To help fight off disease and viruses
Neptune's largest satellite is Triton, and it revolves in a retrograde orbit, meaning to opposite of Neptune's totation<span />
Answer:
(D) the spot could have been caused by an object that emitted a flash that lasted for only a fraction of the time that the camera shutter was open
Explanation:
(A) the spot was not the brightest object in the photograph: The effect described and the brightness of the objects have no relation. Stars of very different brightness will be shown.
(B) the photograph contains many streaks that astronomers can identify as caused by noncelestial objects: Yes, but that doesn't explain the effect described. A plane could leave a streak.
(C) stars in the night sky do not appear to shift position relative to each other: True, at least for relative short times, but that has nothing to do with the effect described, which happens in a very short period of time.
(E) if the camera shutter had not been open for an extended period, it would have recorded substantially fewer celestial objects: True, but quantity of objects does not relate with the particular case described.
(D) the spot could have been caused by an object that emitted a flash that lasted for only a fraction of the time that the camera shutter was open: True, this can happen, for example, with Iridium satellites, they emit a flash (reflect solar light) that lasts a very short time as seen from one point on the surface (the place where the camera is), and something like this could have been captured by the camera shutter, appearing like a point compared to the streaks left by the stars.
Answer
given,
wavelength (λ)= 500 n m
thickness of film= 10⁻⁴ cm
refractive index = μ = 1.375
distance traveled is double which is equal to 2 x 10⁻⁴ cm
a) Number of wave
N = 2.91
N = 3
b) phase difference is equal to
Reflection from the first surface has a 180° (½λ) phase change.
There is no phase change for the 2nd surface reflection and there is no phase difference for the 2nd wave having traveled an exact whole number of waves.
net phase difference = 
= 270°
