The velocity is 60 because you divide your distance by your time (240÷4=60)
Answer:
i)20369 photons
ii) 40 ps
Explanation:
Momentum of one Sodium atom:

In other to stop it, it must absorb the same momentum in photons:

Now, for the minimun time, we use the speed of light and the wavelength. For the n photons:

Answer:
gravitational waves are ripples in spece-time caused primarily when objects are accelerated and the energy for the acceleration is transpoted as gravitational radiation.
they are difficult to detect because they require very sensitive technology or you will have to wait unitl black holes collide.