Question

What is the energy in J of a photon of light with a frequency of 1060 Hz? Please sure to answer with correct number of significant figures and use unit after the number.

Explain what is meant by atomic (line) spectrum. (Give the experimental conditions necessary for its observation.)

Then use Planck's quantum theory to explain why the spectrum is not continuous.

Answer 1

Sol: Energy of photon is given by, E = h

Here h is the planck's constant ( 6.626 × 10^(-34) Js) and is frequency.

E = 6.626 × 10^(-34) × 1060 = 7023.56 × 10^(-34) J

Atomic spectrum: When sample of atoms are energised or excited by either heating or by light then electrons in an atom excited to higher energy state and when they come back to lower energy state then they emits radiation which on splitting give a atomic or line spectrum.

Conditions: 1. Arms of spectrophotometer should be aligned horizontal to radiation obtained.

2. Instrument must be calibrated.

According to the Planck's quantum theory , any species like atom or molecule can absorb or emit radiation in discrete quantities of energy as there are some energy differences between the energy states or levels in an atom or molecules which are responsible for that. Therefore the spectrum obtained from an atom or molecule is always discontinuous as there is no continuation in energy gap between energy states in an atom or molecules.