Answer:
The distance from the radio station is 0.28 light years away.
Solution:
As per the question:
Distance, d = 4 ly
Frequency of the radio station, f = 854 kHz = 
Power, P = 50 kW = 

Now,
From the relation:
P = nhf
where
n = no. of photons/second
h = Planck's constant
f = frequency
Now,

Area of the sphere, A = 
Now,
Suppose the distance from the radio station be 'r' from where the intensity of the photon is 



Now,
We know that:
1 ly = 
Thus

Answer : Celestial or azimuth - altitude
Explanation :
Celestial : The celestial coordinates that are analogous to longitude and latitude are called RA and Dec.
RA = Right Ascension
Dec = Declination
RA is the measured in unit of time and Dec is measured in degree.
The equatorial coordinate system is the projection of the latitude and longitude coordinate system on the celestial sphere.
Azimuth - altitude : Azimuth - altitude define the location of an object in the sky.
The altitude is the distance of an object appears to be above the horizon.
The Azimuth of the object is the angular distance along the horizon to the location of the object.
Answer:

Definition:
Half-life- The time taken for half of the radioactive isotopes to decay.
Explanation:
How does radioactive decay work? Radioactive decay is a process by which unstable nuclei become more stable through the emission of alpha or beta particles or gamma rays.
Since a half-life is the time taken for half of the isotopes to decay, we can simply divide the initial mass of 100 grams by 2; this gives us 50 grams.
1) Divide 100g by 2.
