Why is it necessary to collimate the light source before using the prismto disperse the light? blue light is bent more by a prism than orangelight. does blue light or orange light have a larger index of refractionin glass? which color has the larger wavelength, orange or blue?

Why is it necessary to collimate the light source before using the prism to disperse the light?

To get parallel rays and have a better decomposition.

Blue light is bent more by a prism than orange light. Does blue light or orange light have a larger index of refraction in glass?

Blue light has larger index of refraction in the glass.

Which color has the larger wavelength, orange or blue?

Orange has a larger wavelength.

Explanation:

Stars radiate light in all directions, this divergent pattern is collimating by, for example, a slit before it reaches the prism, so in that way the rays will be in parallel form making easier to decompose light (The separation between its characteristic colors will be more accentuated).

Blue light has a value of 1.528 of index of refraction while red light has a value of 1.513 (close to the value of orange light). That means the blue light is more refracted by the glass (greater angle of refraction¹). To understand, it is necessary to define the index of refraction:

  (1) 

Where c is the speed of light in vacuum and v is the speed of light in the media.

In the case of blue light, the size of its wavelength is compared with the size of the particles in the media, so it will have a greater interaction than orange light which have a larger wavelength. As a result, it is gotten a slower speed in the blue light and the propagation differs from its original path.

¹Refraction: The change in speed and propagation of light as a consequence of passing from one media to another.

neither accurate nor precise.