Final answer:
Calculating the angle of deviation for a light ray incident on an equilateral prism requires the use of Snell's Law and the geometry of the prism, usually involving the prism's formula. The same deviation will occur at one other specific angle where the light passes symmetrically through the prism, which is known as the angle of minimum deviation.
Step-by-step explanation:
To calculate the angle of deviation produced by an equilateral prism with a refractive index of 1.55 when a light ray is incident at an angle of 40°, we would need to use Snell's Law and the geometry of the prism. However, without the specific formula or a more detailed explanation of the geometry involving an equilateral prism, we can't provide an exact answer to this part of the question. Nevertheless, for a detailed explanation and calculation, one would typically need to know the angle of refraction inside the prism, use this to determine the path of the light through the prism, and finally, apply the prism formula (which considers the refractory index, the angle of incidence, the angle of refraction, and the apex angle of the prism) to find the deviation angle.
Regarding the second part of the question, the deviation will be the same for another angle of incidence if the light ray undergoes minimum deviation, which occurs when the light ray passes symmetrically through the prism. At this point, the angle of incidence equals the angle of emergence, and due to the symmetry, this would be the only other angle of incidence to provide the same angle of deviation. Specific calculation for this requires utilizing the prism's minimum deviation formula.