Explore the relationship between the energy levels in materials and the spectrum of the emitted light. This package contains four different programs, each corresponding to an entirely different physical situation, the only similarity being that in each case the spectrum of emitted light is presented.

The Gas Lamps module presents the relationship between the discrete energy levels in a gas and the spectrum of the light emitted by a gas discharge tube. Choose from a given set of gases or construct the spectrum of a hypothetical gas. Next, create an energy level diagram for the gas which would result in the given spectrum.

The LED module extends the idea of the spectrum of the emitted light to from gas discharge tubes, which have a discrete spectrum resulting from a discrete set of allowed energy levels, to the continuous spectrum of an LED which result from an energy band. Observe the relationship between the energy band gap of an LED and the spectrum of the emitted light for a range of different LEDs.

The Luminescence module is useful in learning about various luminescence phenomena. The Fluorescence program explains the working principle of fluorescent light sources. Adjust the energy of the excited and metastable state, as well as the energy of the input light. The program displays the energy of the emitted light. Use the program to understand the relationship between the emitted light and the energy level in the fluorescing material.

Use the Infrared Detector program to study the principle of the infrared detector card which is commonly used by TV repair persons to determine whether the remote control works. Observe that for an IR detector card to work the electrons have to be pumped up to an intermediate energy level where they gain additional energy from the IR light before loosing all the energy to visible light.

The Phosphorescence program is used to understand the mechanism of phosphorescence and the related electronic transitions. In this program the user exposes a toothbrush of phosphorescent material to light causing the electrons to go into an excited state. The toothbrush is then immersed in liquid nitrogen, which causes the electrons to drop into a metastable state. Next, the user exposes this toothbrush to a heat lamp. By adjusting the temperature of the heat lamp, the user can provide sufficient energy to cause the transition from the metastable to the excited state, from where the electrons drop back to the ground state emitting light, which is phosphorescence.

The Lasers module enables the user to understand how lasers work. This program simulate two different lasers: ruby laser and helium-neon laser. In either case the user can explore the relationship between spectrum of light emitted by the laser and the

In the Ruby Laser program the user adjusts the excited and metastable state energies of the material and turns on the energizing source. If the energy of the source is greater than that of the excited state a transition appears from the ground to the excited state. If not, the user receives a message to increase the energy of the input light and/or decrease the energy of the excited state. The program then displays the transition to the excited state, the non-radiative transition to the metastable and finally the transition from the metastable to the ground state which causes the lasing action.

In the Helium-Neon Laser program, the user adjusts the various energy levels in the energy level diagram for the helium and neon atoms. Next the user provides the energy from the input source which causes a transition to the excited state of helium. The motion of the helium and neon atoms and their consequent collision causes a transmission of this energy to the neon atoms. This causes a transition within the neon which is responsible for the lasing action.

The correct spectra of both the ruby and helium-neon lasers are displayed in the respective modes, and the user can adjust the various energy levels in each case to obtain the desired spectrum.

Thus, in general, this software package is invaluable in understanding the relationship between energy levels and the spectrum of emitted light in a variety of different situations.

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