I believe that the answer is C<span />
He performed a streak test, in which a piece of the mineral is rubbed across a piece of unglazed porcelain in order to determine the color of the mineral in powdered form.
Answer:
Answer is A, it will pass through to focal point after reflecting.
Explanation:
I had the same question in a test, Sorry that you had to do this question in middle school.
Answer:
a) 0.477 W/m²
b) 13.407 N/C
c) 18.96 N/C
Explanation:
P = Power = 150 W
r = Distance = 5 m
ε₀ = Permittivity of space = 8.854×10⁻¹² F/m
a) Average intensity
![\bar{S}=\frac{P}{A}\\\Rightarrow \bar{S}=\frac{150}{4\pi r^2}\\\Rightarrow \bar{S}=\frac{150}{4\pi 5^2}\\\Rightarrow \bar{S}=0.477\ W/m^2](https://tex.z-dn.net/?f=%5Cbar%7BS%7D%3D%5Cfrac%7BP%7D%7BA%7D%5C%5C%5CRightarrow%20%5Cbar%7BS%7D%3D%5Cfrac%7B150%7D%7B4%5Cpi%20r%5E2%7D%5C%5C%5CRightarrow%20%5Cbar%7BS%7D%3D%5Cfrac%7B150%7D%7B4%5Cpi%205%5E2%7D%5C%5C%5CRightarrow%20%5Cbar%7BS%7D%3D0.477%5C%20W%2Fm%5E2)
∴ Average intensity is 0.477 W/m²
b) Rms value
![\bar{S}=c\epsilon_0E_{rms}^2\\\Rightarrow E_{rms}=\sqrt{\frac{\bar{S}}{c\epsilon_0}}\\\Rightarrow E_{rms}=\sqrt{\frac{\bar{0.477}}{3\times 10^8\times 8.854\times 10^{-12}}}\\\Rightarrow E_{rms}=13.407\ N/C](https://tex.z-dn.net/?f=%5Cbar%7BS%7D%3Dc%5Cepsilon_0E_%7Brms%7D%5E2%5C%5C%5CRightarrow%20E_%7Brms%7D%3D%5Csqrt%7B%5Cfrac%7B%5Cbar%7BS%7D%7D%7Bc%5Cepsilon_0%7D%7D%5C%5C%5CRightarrow%20E_%7Brms%7D%3D%5Csqrt%7B%5Cfrac%7B%5Cbar%7B0.477%7D%7D%7B3%5Ctimes%2010%5E8%5Ctimes%208.854%5Ctimes%2010%5E%7B-12%7D%7D%7D%5C%5C%5CRightarrow%20E_%7Brms%7D%3D13.407%5C%20N%2FC)
∴ Rms value of the electric field is 13.407 N/C
c) Peak value
![E_0=\sqrt 2E_{rms}\\\Rightarrow E_0=\sqrt 2\times 13.407\\\Rightarrow E_0=18.96\ N/C](https://tex.z-dn.net/?f=E_0%3D%5Csqrt%202E_%7Brms%7D%5C%5C%5CRightarrow%20E_0%3D%5Csqrt%202%5Ctimes%2013.407%5C%5C%5CRightarrow%20E_0%3D18.96%5C%20N%2FC)
∴ Peak value of the electric field is 18.96 N/C