How to calculate the wavelength?

Answer 1

This question is from Bohr's atomic model. The total length of the orbit is an integral multiple of the wavelength of an electron. The relation given by 2(pi)(radius)=n(wavelength), where n is the principal quantum number. Proof of this came later from De-Broglie's hypothesis,

(wavelength)=h/(linear momentum)

It is-

(wavelength)=h/mv .....I

From Bohr's model (Quantization of angular momentum),

mvr=nh/2(pi)

So,

2(pi)r=n(h/mv)

From I,

2(pi)r=n(wavelength)

Answer 2

frequency = Speed of light/ wavelength