Enemy or foe is an individual or a group that is seen as forcefully adverse or threatening. The concept of an enemy has been observed to be basic for both individuals and communities.
A diffractometer (pronunciation: di-frak-'tÃ¤-m&-t&r) is a measuring instrument for analyzing the structure of a material from the scattering pattern produced when a beam of radiation or particles (such as X-rays or neutrons) interacts with it. Principle
Your doctor will use a retinoscope or auto-refractor to measure your refraction without asking for subjective responses from you. 1  Retinoscopy: One of the most common instruments used for objective refraction is the retinoscope. Using a retinoscope, your doctor will project a streak of light into your pupil. A series of lenses are flashed in front of your eye. By looking through the retinoscope, your doctor can study the light reflex of the pupil.