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askphysicslogoAccording to the theory of relativity, the length will decrease to zero.

Please refer to ther following links for more information on the question.

  1. http://en.wikipedia.org/wiki/Length_contraction
  2. http://io9.com/5527521/what-happens-if-youre-traveling-at-the-speed-of-light-and-turn-on-your-headlights
  3. http://wiki.answers.com/Q/What_happens_when_you_travel_at_the_speed_of_light
  4. http://www.physics.org/interact/time-twins/special-relativity.html
  5. http://www.physlink.com/education/askexperts/ae169.cfm
Time dilation in transversal motion. The requi...
Time dilation in transversal motion. The requirement that the speed of light is constant in every inertial reference frame leads to the theory of relativity (Photo credit: Wikipedia)

Continuity of Magnetic Field Lines

I was taught in school that magnetic lines can not cross each other without breaking. Also i was taught that magnetic field lines are unidirectional traveling out of the north end of the magnetic field and connecting to the south magnetic pole. My question is, In the event of the lines being broken, would the broken or open north magnetic lines coming out of the north pole of the magnetic field( traveling at the speed of 186,000 miles per second, the speed of light) be able to connect with any other south magnetic poles they encounter even a second or more away.thank you, Ron G.


Diagram of Earth's magnetic field lines includ...


Angle between acceleration and velocity in projectile motion

What is the angle between the directions of  acceleration and velocity at the highest point of projectile?


At the highest point of a projectile, the vertical component of velocity is zero and the velocity is entirely horizontal. The direction of acceleration (due to gravity) is vertically downwards throughout the motion of the projectile.

Therefore, the angle between the direction of acceleration and velocity at the highest point of a projectile is 90 °

Motion of connected system – A numerical problem

What is the acceleration of the body m2 in the diagram below?

(The question was posted by Shuvam Shukla. Students and other visitors can post solution as comments to this post)

Why light is not accelerated in vacuum?

If vacuum has no mass …. then why isn’t a light beam accelerated in space ?? – Asks Akil Raj


The speed of light in a medium or in vacuum is constant. It is neither accelerated or decelerated while propagating. But, the speed of light in a (optically) denser medium is less than the speed of light in an optically rarer medium.

The speed of light is maximum in vacuum and it is constant and is equal to 299792458 m/s as theoretically established by electromagnetic wave theory too.

9If you look at it this way; “In vacuum there is no particle to oppose the propagation of light, therefore it should travel with a constant velocity, because to increase or decrease the velocity some external influence is essential)

Huygens Wave Theory and rectilinear propagation of light

As per 12th Physics textbook, it has been mentioned that according to Huygens wave theory of light, light does not travel in straight line.

But I have heard that it is wrong and rectilinear propagation of light is one of the merits of Huygens theory rather than demerit please clear my doubt

Asked by Mohammed Faiz Ansari


The wave nature of light becomes prominent only when the size of the aperture of the obstacle is comparable to the wavelength.

The light of wavelength λ coming through an aperture of width a can be considered to be in rectilinear motion up to a distance of


where ZF is called the Fresnel distance.


Thus, wavelength λ decreases, the limit for rectilinear propagation increases.This is the reason why we say, ray optics is valid when the limiting case wavelength λ tending to zero is applied.

on Einsteins research

Albert Einstein

if the papers of Einstein depend upon speed of light as its base, and the particles which have speed greater than the light could pose treat to be it. then in that case why cant that particle could be set as the Einsteins theorms base so that it doesnt violate and simple corrections could correct the theorms!!

(Sajin Asks)

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