a). for velocity, you must have a number, a unit, and a direction.
Yes. This one isn't bad. The 'number' and the 'unit' are the speed.
b). the si units for velocity are miles per hour.
No. That's silly.
'miles' is not an SI unit, and 'miles per hour'
is only a speed, not a velocity.
c). the symbol for velocity is .
You can use any symbol you want for velocity, as long as
you make its meaning very clear, so that everybody knows
what symbol you're using for velocity.
But this choice-c is still wrong, because either it's incomplete,
or else it's using 'space' for velocity, which is a very poor symbol.
d). to calculate velocity, divide the displacement by time.
Yes, that's OK, but you have to remember that the displacement
has a direction, and so does the velocity.
When light travels from a medium with higher refractive index to a medium with lower refractive index, the critical angle is the angle of incidence above which light is reflected only (no refraction occurs), and the value of this critical angle is given by

where n2 is the refractive index of the second medium and n1 is the refractive index of the first medium.
In this problem, the first medium is the glass (

), while the second medium is oil (

), therefore the critical angle is given by
Answer:
λ = 3.62 x 10⁻⁷ m = 362 nm
Explanation:
The grating equation gives the relationship between the wavelength, the diffraction line order and the diffraction angle. The grating equation is written as follows:
mλ = d Sinθ
where,
m = order of diffraction = 6
λ = longest wavelength = ?
d = 1/(460 rulings/mm)(1000 mm /1 m) = 2.17 x 10⁻⁶ m/ruling
θ = Diffraction angle = 90° (for longest wavelength)
(6)λ = (2.17 x 10⁻⁶ m/ruling) Sin 90°
λ = (2.17 x 10⁻⁶ m/rulings)/6
<u>λ = 3.62 x 10⁻⁷ m = 362 nm</u>
Currently, there are no black dwarfs that exist in our universe. Black dwarfs are extremely cool and are almost invisible. They are hypothetical in existence.