Question

Hydrogen atom emits light when it changes from n = 5 energy level to n = 2 energy level. Which colour of light would the atom emit?

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

Answer 1

Answer: (D)

Violet

Answer 2

$\frac{1}{\lambda} = R\left\lbrack \frac{1}{2^{2}} - \frac{1}{5^{2}} \right\rbrack = R\left\lbrack \frac{1}{4} - \frac{1}{25} \right\rbrack = \frac{21R}{100}$

$\therefore\lambda = \frac{100}{21R} = \frac{100}{21 \times 1.1 \times 10^{7}} = \frac{100}{23.1} \times 10^{- 7}m$

$= 4346Å$

This correspond to violet.