Chapter 3, Problem 1E

The light produced by a red neon sign is due to the emission of light by excited neon atoms. Qualitatively describe the spectrum produced by passing light from a neon lamp through a prism.

Interpretation Introduction

Interpretation:

The spectrum produced by passing light from a neon lamp through a prism is to be explained.

Concept introduction:

The distance between consecutive troughs or peaksis said to be the wavelength of any wave and is denoted by λ. The unit of wavelength is meter, cm, nm, mm etc.

The reciprocal of wavelength of any wave is called wave number. It is denoted by $\stackrel{-}{\nu }$ . It is the reciprocal of wavelength thus the unit is also the reciprocal of the unit of wavelength mean ${\text{m}}^{-1},{\text{cm}}^{-1},{\text{mm}}^{-1}{\text{, nm}}^{-1}$ .

  $\begin{array}{l}\text{wave number }=\frac{\text{1}}{\text{wavelength}}\\ \stackrel{-}{\nu }=\frac{1}{\lambda }\end{array}$

Frequency of any wave is the number of oscillations per second means the number of oscillation in one second. It is denoted by ν. The unit of frequency is per second. Its SI unit is Hz , which is equal to ${\text{s}}^{-1}$ .

The energy of a photon is calculated by the Plank’s equation. The equation is following:

  $E=h\nu$

Here, $E=\text{Energy of photon, }h=\text{Plank's constant (6}\text{.626}\times {\text{ 10 }}^{-\text{34}}\text{ J}\cdot \text{s), }\nu =\text{Frequency }$

Spectrum:

The special wavelength of electro-magnetic radiation, which is emitted or absorbed by an object like substance, atom or molecules is known as a spectrum.

Spectrum is mainly two types:

1. Emission spectrum
2. Absorption spectrum

Answer to Problem 1E

The spectrum produced by passing light from a neon lamp through a prism is line spectrum.

Explanation of Solution

When the radiation is emitted from any substance, it is called emission spectrum.

In the type of emission spectrum, light or electro-magnetic radiation directly passed through a prism.

It is mainly divided into three types as follows:

1. Continuous spectrum
2. Line spectrum
3. Band spectrum

The spectra produced from neon is an example of line spectrum, in which spectrum consists of discrete lines corresponding to the wavelength of the colour emitted by the substance. When the radiation which is produced from neon passed through a prism there are multiple lines of brightness of red colour, which indicate it is a line (emission) spectrum.