75.17 mg of the radioactive substance will remain after 24 hours.
Answer:
Explanation:
Any radioactive substance will obey the exponential decay behavior. So according to this behavior, any radioactive substance will be decaying in terms of exponential form of disintegration constant and Time.
Disintegration constant is the rate of decay of radioactive elements. It can be measured using the half life time of the radioactive element .While half life time is the time taken by any radioactive element to decay half of its concentration. Like in this case, at first the scientist took 200 mg then after 17 hours, it got reduced to 100 g. So the half life time of this element is 17 hours.
Then Disintegration constant = 0.6932/Half Life time
Disintegration constant = 0.6932/17=0.041
Then as per the law of disintegration constant:
Here N is the amount of radioactive element remaining at time t and 
is the initial amount of sample, x is the disintegration constant.
So here, = 200 mg, x = 0.041 and t = 24 hrs.
N = 200 ×
=75.17 mg.
So 75.17 mg of the radioactive substance will remain after 24 hours.
Answer:
Electrons.
Explanation:
Electricity was discovered before the discovery of electrons by J.J Thompson in 1896. Before the electron, it was thought that it is the positive ions that move through the wire and carry current—that's why today the conventional current represents the flow of positive charges.
After J.J Thompson's discovery of the electrons, it was realized that it is the electrons that actually carry the current through the conductor. But changing the direction of the conventional current didn't seem appropriate, and that's why the convention continues to be used to this day—reminding us that once it were the positive ions that were thought to carry the current.
Answer:
72,300 years.
Explanation:
- Initial mass of this sample: 504 grams;
- Current mass of this sample: 63 grams.
What's the ratio between the current and the initial mass of this sample? In other words, what fraction of the initial sample hasn't yet decayed?
.
The value of this fraction starts at 1 decreases to 1/2 of its initial value after every half-life. How many times shall 1/2 be multiplied to 1 before reaching 1/8? 
. It takes three half-lives or 
years to reach that value.
In certain questions the denominator of the fraction is large. It might not even be an integer power of 2. The base-x logarithm function on calculators could help. Evaluate
to find the number of half-lives required. In case the base-x logarithm function isn't available, but the natural logarithm function 
is, apply the following expression (derived from the base-changing formula) to get the same result:
.
