To calculate how many photons are in a certain amount of energy (joules) we need to know how much energy is in one photon.
Start by using two equations:
Energy of a photon = Frequency * Planck's constant (6.626 * 10^(-34) J-s)
Speed of light (constant 3 * 10^8 m/s) = Frequency * Wavelength
Which means:
frequency = Speed of Light / Wavelength
So energy of a photon = (Speed of light * Planck's constant)/(Wavelength)
You may have seen this equation as E = hc/<span>λ</span>
We have a wavelength of 691 nm or 691 * 10^-9 meters
So we can plug in all of our knowns:
E = (6.626 * 10^(-34) J-s) * (3.00 * 10^8 m/s) / (691 * 10^-9 m) =
2.88 * 10^(-19) joules per photon
Now we have joules per photon, and the total number of joules (0.862 joules)
,so divide joules by joules per photon, and we have the number of photons:
0.862 J/ (2.88 * 10^(-19) J/photon) = 3.00 * 10^18 photons.
X-rays are found in the given region.
Answer: Option B
<u>Explanation:</u>
The wavelengths of different waves are studied carefully, and their range is determined according to the frequency they exhibited. And based upon the studies, the electromagnetic waves are classified into eight different categories such as gamma, X-, UV, visible, near IR, middle IR, far IR, micro and radio waves.
And each category has different wavelengths and the given radiation falls under X-rays. The wavelength range of X-rays varies from 1 nm to 1 pm. Here, “nm” stands for nano meter and “pm” stands for “pico meter”.
Answer: The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),[note 1] rubidium (Rb), caesium (Cs),[note 2] and francium (Fr).
Explanation: