Chapter 4, Problem 1D

To determine

The meaning of absorption and emission spectrum and their relationship.

Explanation of Solution

Introduction

Spectrum is formed on emission or absorption of light energy by electron. It is a characteristic for particular element. Each element has its own spectra.

Absorption spectrum: The spectrum formed as a result of jump of an electron from lower to higher energy level when energy in form of photon is supplied to it. The absorbed wavelength vanishes from spectrum.

Emission spectrum: The spectrum formed as a result of emission of electron from excited energy level to its ground state. The energy is released in form of a photon. It shows emitted wavelength

Relation between them: Since, energy difference between two energy levels is same while going from upper to lower (emission) or from lower to upper (absorption), frequency of photon is same as energy depends on frequency. Hence color of light is same emitted or absorbed is same for two energy levels.

$\Delta E($ absoption $)=\Delta E$ (emission)

Conclusion

Absorption spectrum is formed when electron jumps from lower to higher energy level and vice-versa for emission spectrum.The frequency of absorbed and emitted light is same for both spectrum.