1. What is spectroscopy?Explain absorption and emission spectra. 2. Describe important characteristics of electromagnetic radiations. Give expression for calculating the energy for a mole of photon?

1. Spectroscopy is the study of the interaction between matter and electromagnetic radiation. It involves the analysis of the absorption and emission of light by matter, which can provide valuable information about the composition, structure, and properties of substances.

Absorption spectra refer to the pattern of absorption of light by a substance at different wavelengths. When light passes through a sample, certain wavelengths are absorbed by the atoms or molecules in the sample, leading to dark lines or bands in the spectrum. These absorption lines are unique to each substance and can be used to identify the presence of specific elements or compounds.

Emission spectra, on the other hand, refer to the pattern of light emitted by a substance when it is excited by an external energy source. When atoms or molecules are excited, they can release energy in the form of light at specific wavelengths, resulting in bright lines or bands in the spectrum. Like absorption spectra, emission spectra are unique to each substance and can be used for identification purposes.

2. Electromagnetic radiation has several important characteristics, including wavelength (λ), frequency (ν), and energy (E). The relationship between these properties is described by the equation:

c = λν

where c is the speed of light in a vacuum (approximately 3.00 x 10^8 m/s), λ is the wavelength of the radiation in meters, and ν is the frequency of the radiation in hertz (Hz).

The energy (E) of a photon can be calculated using the equation:

E = hν

where h is Planck's constant (approximately 6.626 x 10^-34 J·s) and ν is the frequency of the radiation in hertz. This equation shows that the energy of a photon is directly proportional to its frequency, meaning that higher frequency radiation (e.g., ultraviolet or X-rays) has higher energy photons compared to lower frequency radiation (e.g., infrared or radio waves).

For a mole of photons, the energy can be calculated by multiplying the energy of a single photon by Avogadro's number (6.022 x 10^23 mol^-1):

Energy for a mole of photons = (hν) x N_A

where N_A is Avogadro's number.

1. Spectroscopy

Spectroscopy is the study of the absorption, emission, and scattering of electromagnetic radiation by matter. It is a fundamental tool for understanding the structure and dynamics of atoms, molecules, and solids.

Absorption Spectra:

- When electromagnetic radiation interacts with matter, electrons can absorb energy and move to higher energy levels.
- This absorption is detected as a decrease in the intensity of the radiation at specific wavelengths, corresponding to the energy differences between the energy levels.
- The pattern of absorption lines and bands provides information about the energy levels of the absorbing species.

Emission Spectra:

- When electrons in excited energy levels return to lower energy levels, they release energy as photons of electromagnetic radiation.
- The emitted radiation has specific wavelengths, corresponding to the energy differences between the energy levels.
- The pattern of emission lines and bands provides information about the energy levels and electronic transitions of the emitting species.

2. Electromagnetic Radiation

Important Characteristics:

- Wavelength (λ): Distance between adjacent crests or troughs of the wave.
- Frequency (ν): Number of waves passing a fixed point per second.
- Wavenumber (ṽ): Reciprocal of wavelength, expressed in cm^-1.
- Photon: A discrete packet of electromagnetic energy.

Energy of a Mole of Photons:

The energy of one photon is given by:

```
E = hν
```

where:

- E is the energy in joules
- h is Planck's constant (6.63 x 10^-34 J s)
- ν is the frequency in Hz

For a mole of photons, the energy is:

```
E = Nhν
```

where:

- N is Avogadro's constant (6.022 x 10²³ mol^-1)