At speeds approaching the speed of light, time slows down in two ways, which in actuality are the same way observed from two frames of reference. If you're standing still and something is moving close to the speed of light relative to you, time is slower for it. If you're moving at close to the speed of light and everything else is standing still, time is still slower for everything else. Why? Because if you change reference frames from the objects that are standing still's point of view back to your point of view, then it is no longer you that is traveling close to the speed of light, but is in fact everything else that is.
This effect is called time dilation, and has been experimentally verified time and again. The equation to measure how much slower time passes for different reference frames is actually quite simple:
Δt' = Δt/√[1 - (v2/c2)], where v is the relative speed of what's moving compared to that of a stationary observer, c is the speed of light, Δt is the time elapsed by the observer's watch, and Δt' is the time that has elapsed by the object that is moving's watch.
Light does not accelerate. In a vacuum, light always travels at a constant speed of approximately 299,792 kilometers per second, known as the speed of light. It only changes speed when it passes through different mediums.
The constancy of the speed of light in vacuum is the keystone of relativity. Because of this, the frequency/wavelenth of the light changes relative to the observer when the source is approaching or receding from the observer. That's why there is red shift. Usually, this is explained by analogy to the Doppler effect with sound waves, where the speed of sound is constant and the frequency has to changes as the relative motion changes.
Diffraction.
Assuming the speed of light in air is already known (it is close to the speed of light in a vacuum), you might check how the light refracts when it changes from air to water (at what angle), and then use Snell's Law.
Electromagnetic waves, like light, do involve changes in the electric and the magnetic field. These changes propagate at the speed of light - as a wave.Electromagnetic waves, like light, do involve changes in the electric and the magnetic field. These changes propagate at the speed of light - as a wave.Electromagnetic waves, like light, do involve changes in the electric and the magnetic field. These changes propagate at the speed of light - as a wave.Electromagnetic waves, like light, do involve changes in the electric and the magnetic field. These changes propagate at the speed of light - as a wave.
Light does not accelerate. In a vacuum, light always travels at a constant speed of approximately 299,792 kilometers per second, known as the speed of light. It only changes speed when it passes through different mediums.
When light enters a different medium (refracts), its speed changes.
Well... if something changes, it can't be called a constant. And the effects appear not at the speed of light, but when you approach it. What changes is: the time; distances in the direction of travel; the mass of the travelling object.
The speed of light in a vacuum never changes.
The constancy of the speed of light in vacuum is the keystone of relativity. Because of this, the frequency/wavelenth of the light changes relative to the observer when the source is approaching or receding from the observer. That's why there is red shift. Usually, this is explained by analogy to the Doppler effect with sound waves, where the speed of sound is constant and the frequency has to changes as the relative motion changes.
When light enters a different medium, its speed changes as it undergoes refraction. Refraction is the bending of light as it passes from one medium to another, due to the change in speed.
light undergoes refraction when the matter changes the speed of light
The speed of light in a medium changes when the medium of propagation changes. The wavelength and direction of light may also change depending on the medium, due to factors like refraction.
At the speed of light, time does not exist as we understand it. According to Einstein's theory of relativity, time slows down as an object approaches the speed of light, eventually coming to a stop at the speed of light. This means that for light itself, time does not pass.
Time does not stop at the speed of light; rather, time appears to slow down for an object moving at the speed of light relative to an observer.
Diffraction.
The change in speed of light changes the direction.