In history

• The most famous use of a prism was conducted by Isaac Newton, in which he split a beam of white sunlight into its component colors.
  
  

Stellar spectroscopy

• Perhaps the second most famous use of a prism was Edwin Hubble's measuring a red shift in receding galaxies' spectrum, to demonstrate that the universe is expanding. Astrophysicists use such spectra in similar ways today, measuring star distance and searching for black holes by the red shift of nearby stars.
  
  

Reflective prisms in binoculars

• Binoculars use eyepieces to achieve high magnification, but invert the image in the process. Reflections in prisms are used to invert the image once before the eyepiece inverts it back again.
  
  

Atomic spectra

• Atomic phenomena are studied by their spectra, including quantum mechanical effects like Zeeman splitting. Chemists use spectra to identify elements in a flame test.
  
  

Corrective eyeglasses

• A prism in eyeglasses can correct for a deviation of the visual axis, as in diplopia. The two sides of an eyeglass lens are usually parallel. These can be set oblique, as a prism is, to cause a corrective deviation of the image.
  
  

Polarization

• Two prisms of birefringent (double-diffracting) crystal adhered base-to-base can separate a beam into two beams of opposite polarization. Polarization is fundamental in CD players, enabling the laser incident on the CD to be deflected into a detector by a prism it has previously passed through.