An electron in a Bohr model hydrogen atom jumps from the 2nd energy level to the 4th level. Is the photon emitted or absorbed by the atom?

Photon is absorbed by the atom

Explanation:

For an electron to jump from lower energy level to higher energy level it needs some energy. This process can only take place when the atom absorbs energy, which can be in the form of photons. When the electron jumps to higher energy levels, it is known as excited state and it is not stable. So the electron will try to come back to lower energy level and in that process it will release energy.

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.