Suppose two objects are attracting each other gravitationally. if you double the distance between them, the strength of their gravitational attraction

decreases by a factor of 4

Explanation:

Lets take mass of the objects are m₁ and m₂ and the distance between them at initial condition is R.

We know that attraction force between two object given as

G=Constant

If distance become 2 R

R' = 2R

Therefore we can say that gravitational force will become one forth of the initial force.

absorption lines are where light has been absorbed by the atom thus you see a dip in the spectrum whereas.

emission spectra have spikes in the spectra due to atoms releasing photons at those wavelengths.

explanation: