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
Gametic life cycle, as illustrated by diatoms
European wildcat feeding its kittens, as illustrated in Brehm's Life of Animals
Life
the history of life according to fossil records
Ice sheet growth and decay is complex
Plant life cycle