Physics

In a railway track, two rails are joined end to end with a gap in between them because accidents due to expansion in summer can be avoided.

The bending of light as it passes from one medium to another is called refraction. The angle and wavelength at which the light enters a substance and the density of that substance determine how much the light is refracted.

Temperature is the cause of land breeze in general.

Sound levels are measured in decibels(dB), sound level of 80 or more dB can aptly be called noise which can cause serious hearing loss, tensions, high blood pressure, it can induce several disorders prematurely existing, such as hypertension, an increase in blood cholesterol level and is detrimental to health in other aspects when observed for more than maximum tolerable limit of 50 dB._x000D_ Hence, the correct answer is ‘Above 80 dB’.

Neurons (also called neurones or nerve cells) are the fundamental units of the brain and nervous system, the cells responsible for receiving sensory input from the external world, for sending motor commands to our muscles, and for transforming and relaying the electrical signals at every step in between.