Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection.
In acoustics, reflection causes echoes and is used in sonar. In geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water. Reflection is observed with many types of electromagnetic wave, besides visible light. Reflection of VHF and higher frequencies is important for radio transmission and for radar. Even hard X-rays and gamma rays can be reflected at shallow angles with special "grazing" mirrors.
Amsterdam (English /ˈæmstərdæm/; Dutch: [ˌɑmstərˈdɑm] ( listen)) is the largest city and the capital of the Netherlands. Its principal language is Dutch. The city's status as the capital of the nation is governed by the constitution. Amsterdam has a population of 820,256 within city limits, an urban population of 1,209,419 and a metropolitan population of 2,289,762. The city is located in the province of North Holland in the west of the country. It comprises the northern part of the Randstad, one of the larger conurbations in Europe, with a population of approximately 7 million.