Answer: It was known as the SPACE RACE.
Explanation: The space race was a cold war between the Soviet Union (USSR) and the United States (US), to get satellites and humans into space. The competition began in earnest on August 2, 1955, when the Soviet Union responded to the US announcement. On April 12, 1961, the USSR surprised the world again by launching Yuri Gagarin into a single orbit around the Earth in a craft they called Vostok 1.
Answer:
The wavelength of the line in the emission line spectrum of hydrogen caused by the transition of the electron for the given energy levels is 
Explanation:
Given :
The energy E of the electron in a hydrogen atom can be calculated from the Bohr formula:

= Rydberg energy
n = principal quantum number of the orbital
Energy of 11th orbit = 

Energy of 10th orbit = 

Energy difference between both the levels will corresponds to the energy of the wavelength of the line which can be calculated by using Planck's equation.


(Planck's' equation)


The wavelength of the line in the emission line spectrum of hydrogen caused by the transition of the electron for the given energy levels is 
I'm pretty sure it's the same 2mm = 2cc = 2c^2