It is a chemical <em>process</em> - an oxidation.
Answer:
Explanation:
When an electron jumps from one energy level to a lower energy level some energy is released in the form of a photon.
The difference in energy between the two levels is the energy of the photon and that energy is related to the frequency of the photon by the Einstein - Planck equation:
Where,
- E = energy of the photon,
- h = 6.626×10⁻³⁴ J.s, Planck constant, and
- ν = frequency of the photon.
So, to find the frequency you must first find the energy.
The transition energy can be calculated using the formula:
Where E₀ = 13.6 eV ( 1 eV = 1.602×10⁻¹⁹ Joules) and n = 1,2,3,...
So, the transition energy between n = 4 and n = 3 will be:
- ΔE = - E₀ [ 1/4² - 1/3²] = - 13.6 eV [1/16 - 1/9] = 0.6611. . .eV
- ΔE = 1.602×10⁻¹⁹ Joules/eV × 0.6611... eV = 1.0591 ×10⁻¹⁹ Joules
Now you can use the Einstein - Planck equation:
- ν = 1.0591 ×10⁻¹⁹ J / 6.626×10⁻³⁴ J.s = 1.60×10¹⁴ s⁻¹ (rounded to 3 significant figures).
Answer : The correct option is a car's velocity changes from 25 m/s to 20 m/s in 5 seconds.
Explanation :
Acceleration : It is defined as the change in velocity divided by the time.
The formula of Acceleration is,
So, we can calculate the acceleration only for 2nd option which is a car's velocity changes from 25 m/s to 20 m/s in 5 seconds.
In this option, velocities and time are given.
In all the other options, the velocity and time are not given. So, we can not calculate the acceleration.
Hence, the correct option is a car's velocity changes from 25 m/s to 20 m/s in 5 seconds.
Answer:
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If a person knows nothing else about chemistry, he or she will likely know that water is H 2 O. The chemical formula for water is common knowledge, used in advertisements, elementary school science classes, and casual conversation. But more than just a conversation piece, the formula H 2 O can tell a chemist a great deal of information.
Read more: http://www.chemistryexplained.com/Va-Z/Water.html#ixzz5Fqzk3PDR