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:
d. Relative humidity increases.
Explanation:
The expression of relative humidity in terms of absolute humidity, absolute pressure and saturation pression at measured temperature is:

When temperature decreases, the saturation pressure decreases also and, consequently, relative humidity increases. Therefore, the right answer is option D.
When the dust is too thick to penetrate with visible light, such as the Nebula, Radio Waves are used to penetrate the dust. Longer radio waves can completely penetrate the thick cloud cover, allowing scientists to beam radar waves.