Question

What is the colour corresponding to the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from n = 4 to n = 2?

• A. Blue
• B. Red
• C. Yellow
• D. Green

Answer 1

Answer: (A)

Blue

Answer 2

: $\frac{1}{\lambda} = R\left\lbrack \frac{1}{n_{1}^{2}} - \frac{1}{n_{2}^{2}} \right\rbrack = 109677\left\lbrack \frac{1}{2^{2}} - \frac{1}{4^{2}} \right\rbrack cm^{- 1}$

$= 20564.4cm^{- 1}$

$\lambda = \frac{1}{20564.4cm^{- 1}} = 486 \times 10^{- 7}cmor486 \times 10^{- 9}m$

Colour corresponding to this wavelength is blue.