Is a spectral line with wavelength 656.5 nm seen in the absorption spectrum of hydrogen atoms?

During the experiment if you could triple the breakaway magnetic force with all other quantities left unchanged, what is the new value for the critical velocity if it was v0 (initial velocity), initially? (b) now if you halved the radius with all other quantities left unchanged, what is the new critical velocity if it was v0 (initial velocity), initially? (c) if during the experiment, critical velocity quadrupled with all other quantities left unchanged, what is the new breakaway force if its magnitude was initially f0,?

Photons with the highest energy have the longest period

Awave with a frequency of 500 hz is traveling at a speed of 100 m/s.what is the wavelength?