towards the normal
away from the normal
The medium through which it is propagating. For exampl if the sound waves are travelling in air they will move slower than those travelling through a wall speed of sound in solids > speed of sound in liquids > speed of sound in gases
The speed of light in a material medium is slower than the speed of light in a vacuum. This is a consequence of the electromagnetic wave interacting with the atoms and molecules in the medium, a process merits its own question.Of course, this assumes the medium is transparent for the wavelength of light travelling through it.Light waves slow down when they pass through a medium, eg glass or water
Sound travels slower through a medium at low temperatures because the particles in the medium have lower energy and move more slowly, causing sound waves to propagate more slowly. This reduction in particle movement decreases the speed at which sound can travel through the medium.
The Mach number of an object travelling through a fluid is its speed relative to the speed of sound travelling through the same medium. So an aircraft flying at Mach 1 at sea level would be travelling faster than an aircraft flying at Mach 1 at a high altitude (where the air is thinner and sound travels slower). An object travelling at Mach 2 is travelling twice as fast as an object travelling through the same fluid under the same conditions (temperature and pressure). BUT In common usage, Mach 1 is the speed of sound in air, at sea level and 20 deg C.
A less dense medium refers to a substance that has fewer particles or less mass per unit volume compared to another medium. Conversely, a denser medium has more particles or more mass per unit volume. Light travels faster in a less dense medium and slower in a denser medium.
Light bends towards the normal when it enters a medium with a higher optical density because the speed of light is slower in that medium. This change in speed causes the light to change direction. The phenomenon is known as refraction.
Electromagnetic wave, namely, light as it travels through denser medium its speed decreases from its speed when it travels through air or vacuum.
When light goes through any medium other than a vacuum, its speed is normally slower than in a vacuum.
The thicker and denser the medium, the slower sound will travel through it. The density of the medium matters because the denser the substance is, the more material the sound has to vibrate per inch it travels through the substance. This forces it to slow down.
Light travels slower in oil than in a vacuum because oil has a higher refractive index than a vacuum, which causes light to slow down as it moves through the medium. The denser the medium, the slower light will travel.
Sound waves travel slower through gases than they do through solids. This is due to the lower density and elastic properties of gases compared to solids, which affects the speed of sound propagation through the medium.