Question

The change in frequency by scattering (Raman effect) occurs due to of energy between the incident photon and the scattering molecule. (a) release (b) absorption (c) exchange (d) none of these

Short answer

The correct answer is (c) exchange. This is because in the Raman effect, frequency change is due to the exchange of energy between the incident photon and the molecule.

Step-by-step solution

Understand Raman Effect

According to the Raman effect, when light interacts with a molecule, the incident light's frequency changes. This change occurs due to the exchange of energy between the incident photon and the molecule.

Evaluate the options

Now, let's look at the given choices. Release and absorption are essentially the processes that involve the transfer of energy. However, when we look into the Raman effect more closely - it is clear that there is an exchange of energy between the photon and molecule as both transfer energy to each other, leading to the change in frequency.

Choose the correct option

After evaluating, it becomes evident that answer (c) matches the required cause as it refers to the exchange of energy which accurately describes the energy interaction in the Raman effect.

Key concepts

Scattering of Light

When we shine a light on various materials, whether it's the sky or a solid object, the light doesn't just pass through or get absorbed; some of it gets scattered in different directions. This phenomenon is known as the scattering of light. It involves the redirection of light by small particles and imperfections within a material.

Light is made up of particles called photons, and when these photons encounter obstacles or other particles, they bounce off in various directions. However, not all scattered light is the same. In specific types of scattering, such as the Raman effect, the scattered photons can gain or lose energy, which results in a change in their frequency.

Photon-Molecule Interaction

The photon-molecule interaction is central to understanding the Raman effect. A photon is a quantum of light, essentially a packet of energy. When this photon comes into contact with a molecule, it may be absorbed by the molecule, causing the molecule to move to a higher energy state. Alternatively, a molecule in a high energy state may transfer energy to a photon, which gets scattered.

This interaction between light and matter is not simply a one-way transfer of energy but can be a dynamic exchange. Each encounter can be thought of as a miniature 'collision' where energy is redistributed. The peculiar aspect of the Raman effect is that this interaction causes changes in the energy levels of the molecules without causing a transition to a completely different state.

Frequency Change

One intriguing result of the photon-molecule interaction is the frequency change of the scattered light, which is observed in the Raman effect. Frequency is directly related to the energy of the photon thus, a change in energy due to the interaction leads to a change in frequency.

When a photon gives energy to a molecule, the scattered photon emerges with less energy and, consequently, a lower frequency than the incident photon; this is known as Stokes Raman scattering. Conversely, if the scattered photon gains energy from the molecule, it will have a higher frequency, referred to as anti-Stokes Raman scattering. This shift in frequency provides insights into the vibrational modes of the molecules, which can be unique to specific chemical bonds.

Energy Exchange

The core of the Raman effect lies in the energy exchange between the photons and the molecules they encounter. This exchange can be thought of as a 'handshake' where energy is given and taken, leading to the distinctive frequency shifts observed in Raman spectroscopy.

The particular type of energy exchange can tell us a lot about the nature of the material under study. By measuring the frequency shifts in scattered light, scientists can infer information about the molecular structure, chemical composition, and even the physical state of the material. This energy exchange is incredibly useful in various scientific fields, from chemistry to materials science, for identifying substances and understanding their properties.