Answer:
0.0000076 grams
Explanation:
We're given the half life of Tritium to be 12.3 years. In order to find out the amount of substabce remaining:
Let's first find how many 'half lives' are in 250 years.

Now what is half life? It means the time taken for a given quantity of an element to lose half it's mass.
So in 12.3 years we can find that The amount of 250 g of Tritium will be 250/2 = 125 g. In 24.6 years we'll have 125/2 = 62.5 g
So now we can devise a formula:

Where m is the remaining amount and n is th number of half lives in the time given.
Using this formula we can calculate:

Doing this calculation we get:

As we can see a very small value remains.
Answer:
46.22 cm
Explanation:
The focal refraction, fr is given by
The focal red light is given by


and making fr the subject we obtain

fv = 0.945455* 16.70886 cm = 15.79747 cm

Therefore, violet image is approximately 46.22 cm
We can find the average speed of the body by finding the total distance covered, and then dividing it by the total time of the motion.
The total distance covered is:

while the total time of the motion is

So, the average speed of the body is:
When I find a problem like this, I find it helpful to think about what I know and what equation will help me.
The question tells us the frequency of the wave

Hz. We want to work out the wavelength. What equation links these two quantities?
Wave Speed = Frequency x Wavelength
(we know all electromagnetic waves travel at the speed of light in a vacuum)

and then divide by

to get the wavelength.
Wavelength =

m<u />