Answer:

Explanation:
Let's use the decay equation.

Where:
- A is the activity at t time
- A₀ is the initial activity
- λ is the decay constant
We know that 
So we have:




Therefore, the half-life of the source is 6 hours.
I hope it helps you!
Answer:
the definition of civics is the study of the rights and duties of citizenship.
so the answer is B.
hope this helps.
Answer:
minimum number of photon is 4.05 ×
Explanation:
given data
energy = 50 keV = 50 ×
eV = 50 ×
× 1.602×
J
thickness = 10^-3
contrast = 1%
to find out
number of incident photons
solution
we know here equation that is
E = n × h × ν .......................1
put here all these value
50 ×
= n × 6.6×
× c/ 1× 
50 ×
× 1.602×
= n × 6.6×
×( 3 ×
/ 1×
)
solve it and find n
n = 4.05 ×
so here minimum number of photon is 4.05 ×
30 30 30 30 30 30 30 30 30 30
Answer: 40m
Explanation: Distance is a function of speed/ velocity and time.
From the question the velocity along the z axis is given as 20 m/s at t = 0 secs We were ask to calculate the distance travelled when t = 2secs.
Recall that,
Velocity = distance travelled / time
Since we're calculating for distance we make it subject of formula;
Distance travelled = velocity * time
= 20m/s * 2s
= 40meter.