Question

If white light passes through prism,we will see a spectrum. What will happen if a red or blue light will fall on a prism

Answer 1

When white light, which contains the spectrum of wavelengths from roughly 400 nm (blue light) to 700 nm (red light), goes through a glass prism, the wavelengths are separated into a color spectrum due to the wavelength dependence of the index of refraction of the glass.

If red light passes through prism,there would likely be a range of wavelengths associated with that beam, so the emerging light would be slightly dispersed into a “minispectrum” from dark red to reddish orange or orange or even yellowish orange or something, depending on the range of wavelengths.


If this red light or blue light is from Laser source,the spectrum is small.If it is from LED the spectrum is large.

But if your light beam is strictly monochromatic (the constituents of the red beam have equal wavelength-sources for such light are rare) then no spectrum is formed. Only bending takes place.