Answer:
The speed of this light and wavelength in a liquid are 
and 442 nm.
Explanation:
Given that,
Wavelength = 650 nm
Index refraction = 1.47
(a). We need to calculate the speed
Using formula of speed
Where, n = refraction index
c = speed of light in vacuum
v = speed of light in medium
Put the value into the formula
(b). We need to calculate the wavelength
Using formula of wavelength
Where, 
= wavelength in vacuum
= wavelength in medium
Put the value into the formula
Hence, The speed of this light and wavelength in a liquid are and 442 nm.
A magnetic field is actually generated by a moving current (or moving electric charge specifically). The magnetic field generated by a moving current can be found by using the right hand rule, point your right thumb in the direction of current flow, then the wrap of your fingers will tell you what direction the magnetic field is. In the case of current traveling up a wire, the magnetic field generated will encircle the wire. Similarly electromagnets work by having a wire coil, and causing current to spin in a circle, generating a magnetic field perpendicular to the current flow (again right hand rule).
So if you were to take a permenant magnet and cut a hole in it then string a straight wire through it... my guess is nothing too interesting would happen. The two different magnetic fields might ineteract in a peculiar way, but nothing too fascinating, perhaps if you give me more context as to what you might think would happen or what made you come up with this question I could help.
Source: Bachelor's degree in Physics.
The answer is 5. To find the advantage you just divide 20 by 4.
We know,
Speed = Frequency * Wavelength
Speed = 3 * 0.1 m/s [hertz = 1/sec.]
So, your final answer is 0.3 m/s
Hope this helps!!
