Difference between risk and uncertainty

I was watching this lecture from professor Andrew Loo and he presented a compelling analogy to understand the difference between risk and uncertainty.

The analogy goes as follows:

1. urn A with 50 red balls and 50 black balls, pick a color and draw, if you draw your color you win $10,000.
2. urn B with unknown quantities, pick a color and draw, same prize.

The question is how much you are willing to bet?

Conclusions:

1. in urn A, you know the probability distribution right away and can compute the expected value.

2. in urn B, you don't know the distribution (at least, intuitively).

   1. we can compute the expected value and in fact it is the same as in urn A.
   2. what is missing here is that we don't have intuition about this distribution, it is hard to grasp the risk.
   3. when we have no knowledge or no intuition about the risk we call that uncertainty.
   4. risk is quantifiable from the knowledge of the probability distribution.