In the first direct detection of gravitational waves by LIGO in 2015, the waves came from the merger of two black holes. Option B is correct. This is further explained below.
<h3>What are gravitational waves?</h3>
A gravitational wave is simply defined as a ripple in space that is unseen though extremely rapid. Gravitational waves move at light speed. As they pass past, these waves compress and stretch everything in their path.
In conclusion, the merger of two black holes is the first direct detection of gravitational waves.
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It is eight times more than the star A.
<h3>What is luminosity and on which it depends?</h3>
The luminosity of an object is a measure of its intrinsic brightness and is defined as the amount of energy the object emits in a fixed time.
luminousity depends upon the two factors are:
1) The star's actual brightness
Some stars are naturally more luminous than others ,so the brightness level from one star to next star is significantly different.
2) The star distance from us
The more distance of an object the dimmer it appears.
Energy emitted = sAT⁴
where s is stefan constant
A is surface area and T is temperature .
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Answer:
the length of the simple pendulum is 0.25 m.
Explanation:
Given;
mass of the air-track glider, m = 0.25 kg
spring constant, k = 9.75 N/m
let the length of the simple pendulum = L
let the frequency of the air-track glider which is equal to frequency of simple pendulum = F
The oscillation frequency of air-track glider is calculated as;

The frequency of the simple pendulum is given as;

Thus, the length of the simple pendulum is 0.25 m.