Answer:
3.45×10⁻⁴mm (or 0.000345mm)
Explanation:
Use a method called dimensional analysis here. It involves a chain of conversions, so we'll need some conversions to work with.
- 1nm = 1×10⁻⁹m
- 1mm = 1×10⁻³m
- 345nm; which is given
If you knew the conversion from nanometers to millimeters then you could just do it in one step. But I don't, so I won't. Anyways, you put the conversions into fraction form like so:
And then orient them in a way where multiplying the two (or more in other instances) gives you the units you want. In this cas it's millimeters so you'll have:
(345nm)•(1×10⁻⁹m/1nm)•(1mm/1×10⁻³m)
Notice how all the units reduce except for mm. From here you just multiply across and should get 345×10⁻⁶mm which simplifies to 3.45×10⁻⁴mm.
Simple, A. None of the other answers make sense so, A.
Answer:
a) I = 10⁻² W / m², b) β = 104.8 db
Explanation:
a) For this exercise we use the definition of decibels
β = 10 log
where I and Io are the intensities produced and the sound threshold
I₀ = 10⁻¹² W / m²
log \frac{I}{I_o} = β / 10
I = Io
let's calculate
I = 10⁻¹²
I = 10⁻² W / m²
b) each toad produces the same sound for which the total intensity is
I_total = 3 I
I_total = 3 10⁻² W / m²
expressed in decibels
β = 10 log ()
β = 104.8 db