Answer: The correct answer is Option b. Distance.
Explanation:
Scientists and astronomers use this unit to measure the distance in space. A light year is a unit of distance and not time because light travels very fast and it travels a lot of distance in one year.
Light year is basically defined as how far the beam of light travels in a year.
Therefore, this light year is a unit of distance. Hence, the correct option is option b.

Answer:
Modern communication has made our socio-economic life so much better and easier. It is easier now to communicate with someone far away on another continent and even do business and shop online without been physically present at the other end. One of the most important modern means of communication is the internet which has turned the world to a small global village.
Answer:
The refraction of light at the surface of water makes ponds and swimming pools appear shallower than they really are.
Explanation:
so its just the refraction of light at the surface
Answer:
None of the wavelength is in the visible range
Explanation:
Constructive interference of the reflected waves for different wavelengths can be estimated using:
λ
= 2nd/m
where m is 1,2,3, ...
Therefore:
m=1, λ
= 750 nm
m=2, λ
= 750/2 = 375 nm
The limits of eye's sensitivity is between 430 nm and 690 nm. Beyond this range, the eye's sensitivity drops to approximately 1% of its maximum value.
Answer:
f=4Hz
Explanation:
frequency of a wave if it has a wavelength of 3.0 m and a wave speed of 12m/s
v=fλ → f=v/λ
f=12/3
f=4Hz