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NCERT Class XI Chemistry Structure of Atom Solutions

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Question : 13
Total: 67
What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?
Solution:  
According to Rydberg equation,
1
λ
 = R (
1
n12
−
1
n22
)
Here, n1 = 2, n2 = 4 and R = 109677 cm–1
1
λ
 = 109677 (
1
22
−
1
42
) = 009677 (
1
4
−
1
16
) = 009677 (
4−1
16
) = 109677 ×
3
16
cm−1
⇒ λ =
16
109677×3
 =
16
219031
 = 4.86 × 10−5 cm = 486 × 10−9 m = 486 nm
[Since 1 nm = 10−9 m]
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