Alpha century is 4 light years from earth how long would it take for light form alpha centauri to reach earth

Given:

Distance of alpha century = 4 light year

Speed of light = 3 × m

To find:

Time taken by light to reach earth = ?

Formula used:

Distance = speed × time

Solution:

Distance = 4 light year

Converting distance from light year into meter

1 light year = 365 × 24 × 60 × 60

4 light year = 4 × 365 × 24 × 60 × 60× 3 ×

As we know,

Distance = speed × time

s = v × t

Where s = distance

v = velocity

t = time

So,t =

t = }{3 ×

t = 4 × 365 × 24 × 60 × 60 second

t = 4 year

Thus, Time taken by light to reach earth from alpha century is 4 earth year.

unable to answer the rest since your question is incomplete

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.