Right angle prisms are commonly used to achieve a 90° or 180° light path bend. If the prism is rotated 90°, images viewed through the prism will be erected, but reversed left-to-right. This prism can also be used in combination for image/beam displacement applications. In a right-angle prism, a parallel bundle of light waves entering one of the smaller prism faces at a perpendicular angle is reflected from the hypotenuse face and exits through the other leg. It is often used in telescope, periscope and optical system. A right-angle prism with a roof on the hypotenuse surface is called an Amici prism. It is used in a telescope to provide right-handed and erect image.