A 7.50 g sample of potassium-40 was collected. After 8.757 x 10^9 years,
0.05859 g of the sample remained. What is the half-life of potassium-40?

Determine the wavelength of the light absorbed when an electron in a hydrogen atom makes a transition from an orbital in the n=3 level to an orbital in the n=7 level.

In which of these cases are the two wave points considered to be in phase with each other?

Why is nh3 classified as a polar molecule