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zlopas [31]
2 years ago
12

What is the half-life of a radioisotope if it decays to 25% of its original activity in 7 yr?

Chemistry
1 answer:
Pepsi [2]2 years ago
7 0

Answer:

3.5 yrs

Explanation:

If a sample has decayed to 25%, this means 2 half-lives have passed. We are given this is equal to 7 yrs, and it follows that one half life is 3.5 yrs.

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Mutations that neither benefit nor harm the organism have (blank) effect on the organisms survival
Daniel [21]

Answer:

I would say that the mutation has no effect on the organism, as it doesn't help or harm it.

hope this helps :)

Explanation:

3 0
3 years ago
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Snow melting is a physical change. True False
S_A_V [24]

Answer:

false

Explanation:

4 0
4 years ago
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How many photons are produced in a laser pulse of 0.862 J at 691 nm?
Inga [223]
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.

4 0
3 years ago
Why do you think large differences in temperature between the wet bulb and dry bulb thermometers are possible only at higher tem
olganol [36]

Answer:

This is the temperature indicated by a moistened thermometer bulb exposed to the air flow. The evaporation is reduced when the air contains more water vapor. The wet bulb temperature is always lower than the dry bulb temperature but will be identical with 100% relative humidity.

Explanation:

7 0
3 years ago
What does a useful scientific explanation include ??
ArbitrLikvidat [17]

Answer: scientific explanation

Explanation:

A really good scientific explanation should do two main things: It should explain all the observations and data we have. It should allow us to make testable predictions that we can check using future experiments.

7 0
3 years ago
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