Alpha emission is the process results in a change in mass number. Option B is correct.
<h3>What is mass number?</h3>
The total number of protons and neutrons in an atomic nucleus is known as the mass number, often known as the atomic mass number or nucleon number.
It's about the same as the atom's atomic mass, expressed in atomic mass units.
The alpha particle is a helium nucleus with two protons and two neutrons in an alpha decay or alpha emission. The number of protons and neutrons is reduced by two as a result of this action.
The quantity of protons and neutrons is affected by gamma emission descent. Also, while electron capture has no effect on the number of neutrons, it does raise the 1 also number of protons by one.
Alpha emission is the process results in a change in mass number.
Hence option B is correct.
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The number converted is 
Explanation:
In order to convert from the original units to the final units, we have to keep in mind the following conversion factors:



The original unit that we have is

Therefore, it can be rewritten as:

Therefore, since the initial number was 0.779, the final value is

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Electrical energy is your answer.
Answer:
Velocity, v = 0.239 m/s
Explanation:
Given that,
The distance between two consecutive nodes of a standing wave is 20.9 cm = 0.209 m
The hand generating the pulses moves up and down through a complete cycle 2.57 times every 4.47 s.
For a standing wave, the distance between two consecutive nodes is equal to half of the wavelength.

Frequency is number of cycles per unit time.

Now we can find the velocity of the wave.
Velocity = frequency × wavelength
v = 0.574 × 0.418
v = 0.239 m/s
So, the velocity of the wave is 0.239 m/s.