Silver Cave

Yangshuo County (simplified Chinese: 阳朔县; traditional Chinese: 陽朔縣; pinyin: Yángshuò Xiàn) is a county in Guilin, Guangxi Province, China. Its seat is located in Yangshuo Town. Surrounded by karst peaks and bordered on one side by the Li River (漓江) it is easily accessible by bus or by boat from nearby Guilin. In the 1980s, the town became popular with foreign backpackers, and by the late 1990s packaged tourists began arriving in greater numbers. At that time, domestic tourism represented only a small fraction of the tourists but by 2005 domestic tourists outnumbered foreign tourists by a great margin. Today, the town has become a resort destination for both domestic and foreign travelers.

A cave or cavern is a natural underground space large enough for a human to enter. Caves form naturally by the weathering of rock and often extend deep underground. The word "cave" can also refer to much smaller openings such as sea caves, rock shelters, and grottos.

It is estimated that the maximum depth of the cave cannot be more than 3,000 meters: deeper caves are crushed by the weight of overlying rock. For karst caves the maximum depth is determined on the basis of karstovaniya (the lower limit of karst marking processes, coinciding with the base sequences limestone), which may be lower than the basis erosion due to the presence of siphon channels.

Speleology is the science of exploration and study of all aspects of caves and the environment that surrounds the caves. Exploring a cave for recreation or science may be called caving, potholing, or, in Canada and the United States, spelunking (see caving).

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.

Specular reflection is the mirror-like reflection of light (or of other kinds of wave) from a surface, in which light from a single incoming direction (a ray) is reflected into a single outgoing direction. Such behavior is described by the law of reflection, which states that the direction of incoming light (the incident ray), and the direction of outgoing light reflected (the reflected ray) make the same angle with respect to the surface normal, thus the angle of incidence equals the angle of reflection ( in the figure), and that the incident, normal, and reflected directions are coplanar. This behavior was first discovered through careful observation and measurement by Hero of Alexandria (AD c. 10–70).

Guilin (Chinese: 桂林; Zhuang: Gveilinz) is a prefecture-level city in the northeast of the Guangxi Zhuang Autonomous Region, People's Republic of China, situated on the west bank of the Li River, and bordering Hunan to the north. Its name means "forest of Sweet Osmanthus", owing to the large number of fragrant Sweet Osmanthus trees located in the city. The city has long been renowned for its unique scenery of Karst topography and is one of China's most popular tourist destinations.