C, they didn't know any better
Your answer will be Radio Waves .
That seems to be the only to make sense. Hope that helps u
The radius of a nucleus of hydrogen is approximately

, while we can use the Borh radius as the distance of an electron from the nucleus in a hydrogen atom:

The radius of a dime is approximately

: if we assume that the radius of the nucleus is exactly this value, then we can find how far is the electron by using the proportion

from which we find

So, if the nucleus had the size of a dime, we would find the electron approximately 500 meters away.
Answer:
When light travels from one medium to another, the frequency of light does not change. However, the velocity and wavelength change.
Explanation:
Pls mark me as brainliest
Answer:
Positive z direction.
Explanation:
The magnetic force acting on the electron is given by the formula as :

q is the charge on proton
v is the speed of proton
B is the magnetic field
It is mentioned that the proton is moving with a velocity in the positive x-direction. The uniform magnetic field B in the positive y-direction such taht,
q = +e
v = vi
B = Bj

Since, 

So, the magnetic force acting on the proton in positive z axis. Hence, the correct option is (d) "positive z direction".