Wave plates, also known as retarders, are essential optical components made of birefringent materials that are designed to manipulate the polarization state of light. A waveplate alters the phase relationship between orthogonal components of polarized light, introducing a specific phase retardance. In this article, we will help you to understand quarter wave plates and half wave plates, how quarter waveplates and half waveplates change the polarization states, and explain the uses of quarter wavelength plates and half wavelength plates.