Two radioactive isotopes, X and Y, both decay to stable products. The half-life of X is about a day, while that of Y is about a week.
Suppose a radioactive sample consists of a mixture of these two nuclides. If the mixture is such that the activities arising from X and Y are initially equal, then a few days later the activity of the sample will be due
A) predominantly to Y. B) to X and Y equally.
C) predominantly to X. D) entirely to Y.
Question 2
A tank holds a 1.44-m thick layer of oil that floats on a 0.96-m thick layer of brine. Both liquids are clear and do not intermix.
Point O is at the bottom of the tank, on a vertical axis. The indices of refraction of the oil and the brine are 1.40 and 1.52, respectively. A ray originating at O crosses the brine-oil interface at a point 0.60 m from the axis. The ray continues and emerges into the air above the oil. What is the angle that the ray in the air makes with the vertical?
A) 54 B) 51 C) 60 D) 48 E) 57
The Many Faces of Life
Jan de Heem, Still Life with Lobster.
In pretend play, toy figures and animals “come to life” and interact with each other.
Eggs, milk, and cheese are complete proteins, because they are animal products.
Which reaction below represents Th decay by alpha emission?
Half-life explained