NTNUJAVA Virtual Physics Laboratory
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Easy Java Simulations (2001- ) => optics => Topic started by: ahmedelshfie on May 22, 2010, 12:17:30 am

Title: Dispersion of light with prism
Post by: ahmedelshfie on May 22, 2010, 12:17:30 am
This following applet is Dispersion of light with prism
Created by prof Hwang Modified by Ahmed
Original project Dispersion of light with prism (http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=415.0)

When the light passes from one media into another media, the light beam is bent or refracted according to Snell's Law and the index of refraction of the material.
The speed of light is slower in various materials than it is in a vacuum.
The index of refraction of the material is defined as n=\frac{c}{v}, where c is the speed of light in vacuum and v is the speed of light in the material. The light is refracted because the speed of light is changed at the boundary.

The speed of light through a material varies slightly with frequency of the light. Thus, light with different frequency are refracted at a slightly different angle. This spreading out of the beam of light is called dispersion or chromatic dispersion.
Normally, we only see light with wavelength between 400nm-700nm. (This is the wavelength of light in vacuum, when light enter a material, the wavelength of light will changed because the speed of light is changed while the frequency of the light is always the same.)
 The following applet show light enter a prism with different refraction index for different color of light (red:1.513,1.514,yellow:1.517,green:1.519,blue:1.528,1.532)

You can drag the arrow with mouse to change the location and direction of the light.
Angle of the prism can be adjusted with dslider bar.
Click play to see the slow motion of light and see the dispersion occurs.
When the simulation is paused. You can change the direction of light, click play again to see another dispersion effect.

Title: Re: Dispersion of light with prism
Post by: ahmedelshfie on October 02, 2010, 12:30:20 am
This applet is Prism: Reflection and refraction design by prof Hwang
URL applet Prism: Reflection and refraction (http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=37.0)

Title: Re: Dispersion of light with prism
Post by: ahmedelshfie on October 21, 2010, 05:59:13 pm
In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism  with a triangular base and rectangular sides, and in colloquial use "prism" usually refers to this type.
Some types of optical prism are not in fact in the shape of geometric prisms. Prisms are typically made out of glass, but can be made from any material that is transparent to the wavelengths for which they are designed.
A prism can be used to break light up into its constituent spectral colors (the colors of the rainbow). Prisms can also be used to reflect light, or to split light into components with different polarizations.
How prisms work
Light changes speed  as it moves from one medium to another (for example, from air into the glass of the prism). This speed change causes the light to be refracted and to enter the new medium at a different angle (Huygens principle). The degree of bending of the light's path depends on the angle that the incident beam of light makes with the surface, and on the ratio between the refractive indices of the two media (Snell's law). The refractive index of many materials (such as glass) varies with the wavelength or color of the light used, a phenomenon known as dispersion. This causes light of different colors to be refracted differently and to leave the prism at different angles, creating an effect similar to a rainbow. This can be used to separate a beam of white light into its constituent spectrum of colors. Prisms will generally disperse light over a much larger frequency bandwidth than diffraction gratings, making them useful for broad-spectrum spectroscopy. Furthermore, prisms do not suffer from complications arising from overlapping spectral orders, which all gratings have.
Prisms are sometimes used for the internal reflection at the surfaces rather than for dispersion. If light inside the prism hits one of the surfaces at a sufficiently steep angle, total internal reflection occurs and all of the light is reflected. This makes a prism a useful substitute for a mirror in some situations.