Question

Prisms

Answer 1

so i know that violet refracts the most because of its shorter wavelengths and red refracts least because its longer wavelengths.


but what does the speed of violet and red have to to with the angle of refraction. violet is slower which results in bigger frefraction, red is faster results in small refraction...... confused at THIS part

Answer 2

Imagine this:
Take a piece of glass. The speed of light is slower in glass, and the speed in glass depends upon the wavelength. This I think you already know.
Set the glass so it is level and the light is coming in from the upper left and about 30 degrees to the plane of the upper surface of the glass (and angle of incidence of 60 degrees). We will make the light a single beam of white.
Note: in optics, the side of glass or a lens the light first impacts is called the "first surface". The next interface or exit surface is called the "second surface", etc.
When the light enters the first surface of the glass the EMR (Electro Magnetic Radiation) components (electrical field v. magnetic field) will travel through the glass at a different speed. The vertical component travels at the same (albeit reduced) speed at all wavelengths but the horizontal component moves slower as the frequency increases (aka the wavelength gets shorter).
To imagine this, draw 2 vectors for each color. Each vector starts at the point that the light beam impacts the first surface. The horizontal vector (drawn to the right and parallel to the first surface) is shorter for shorter wavelengths (violet) and longer for longer wavelengths (red). The vertical vector (drawn downward from the point of impact) is the same length for all wavelengths. When summed for any given wavelength, the resultant vector is more "vertical" for shorter wavelengths and more "horizontal" for longer wavelengths. How vertical or horizontal indicates how much bending the light is subjected to. Also note that the length of the resulting vector is shorter for shorter wavelengths of light indicating that shorter wavelengths are traveling through the glass at a total slower speed.
If the piece of glass has parallel sides, all beams will arrive at the second surface at the same time (vertical vectors being the same), just at different points. The light, when exiting the glass back into air or vacuum would bend the shorter wavelength more than the longer wavelengths and the resulting light would exit the glass at nearly the same angle it came in at. Regardless of any error, all wavelengths will exit at an angle approximating the angle of incidence at the point of impact. Very little prismatic effect can be seen. Example: When looking through a window the images from the side look only slightly different from those that are straight ahead.
When a beam of light "enters" a Prism's first surface, it will perform in the same way but when it gets to the other side, the second surface is not at the same angle as the first surface so each wavelength will exit the prism with a different angle relative to the second surface. The higher the difference in the angle between the first and second surfaces, the greater the difference in angles for the different wavelengths of light. The greater the angle of incidence to the first surface, the greater the difference in angles for the different wavelengths of light. Also, a thicker prism will separate the light better at the exit points.
Does that make sense?

Answer 3

OK thanks just one more question so my text book says that for red its 700nm green is 500nm and violet is 350 nm in wavelength. but my teacher says its 750 nm, 500nm and 400nm i just dont know which ones right... @mstoldegon

Answer 4

This one is easy - they are both right. There is no absolute definition for any particular color, it depends upon how that "color" is going to be used. When looking at the colors in a prism, some would put Red near the point at which it is nearly invisible (infrared) while others would put it at the brightest "red" that does not look too dim (like that near infrared) nor looks like a orangish-red.
Rainbows, another form of the spectrum of colors similar to those of a glass prism, were divided (albeit somewhat arbitrarily) into 7 colors: Red, Orange, Yellow, Green, Blue, Indigo, and Violet. Indigo and violet are very difficult for the human eye to see but when the spectrum was evenly divided in seven parts, these were the color designations that were chosen. If one chose the center of each division as the designated wavelength for that color, that wavelength will not match the wavelengths for colors that are specified for the same color names in Print, Color Monitors, Projectors, etc. - and these don't usually agree with each other also.
OK?

Answer 5

OK thanks!