A standing wave having 3 nodes and 2 antinodes is formed between two atoms having a distance $1.21 Å$ Å between them. The wavelength of the standing wave is

• Correct answer
  A

  $1.21 Å$
• B

  $1.42 Å$
• C

  $6.05 Å$
• D

  $3.63 Å$

Solution

Key Idea The given standing wave has 2 segments. The given standing wave is shown in the figure.
As length of one loop or segment is $\frac{\lambda}{2}$, so length of 2 segments is $2\left(\frac{\lambda}{2}\right)$. $\therefore \quad 2 \frac{\lambda}{2}=1.21 Å$ $\Rightarrow \quad \lambda=1.21 Å$

Hence, the correct answer is option: 'A'.