StudentAidUnit 20: Atomic Spectra — Numericals
12th Class Physics · Unit 20: Atomic Spectra
20.1.Find the speed of the electron in the first Bohr orbit.
Given
Bohr orbit
n = 1
Formula
Bohr velocity formula
vn = 2pi k e2h n
Working
Substituting values for n = 1
v1 = 2 × 3.14 × (9 × 109) × frac{(1.6 × 10-19)2}{6.63 × 10-34
Evaluating numerator and exponents
= frac{56.52 × 2.56 × 10-29{6.63 × 10-34 = frac{144.69 × 10-29{6.63 × 10-34
Dividing coefficients and powers of 10
= 21.82 × 105 = 2.182 × 106 m/s
Result
Speed of electron
v1 = 2.19 × 106 ms-1