A seismographic station receives S and P waves from an earthquake, separated in time by 16.6 s. Assume the waves have traveled over the same path at speeds of 4.50 km/s and 8.00 km/s. Find the distance from the seismograph to the focus of the quake.

atomic = no of protons.

mass number-atomic number = neutron number

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

im srry but ur wrong the answer is d a smooth rock, some red dirt, and an empty bird's nest.