I was drawing a spacetime diagram to relate Doppler shift effect but i stuck at a point which i can't understand(adsbygoogle = window.adsbygoogle || []).push({});

This is what I'm trying to draw

An object with mirror is moving away from me with a velocity of 50% speed of light

When each second passes in my clock i send light pulses at that object.

I sent 4 light pulses in 4 second.

The object starts when t=0 in my clock

When t=1 in my clock that object will be ’half light second away’ at the same time t=1 i sent my first light pulse. So in my clock the first light pulse must hit the object when t=2 in my clock (when t=2 in my clock the object will be 1 light second away)

When t=2 i sent my 2nd light pulse and it must hit the object when t=4 in my clock

When t=3 i sends my 3rd light pulse & it must hit the object when t=6 in my clock

Finally t=4 i sends my 4th light pulse and it must hit the object when t=8 in my clock

So i draw my spacetime diagram and drew a 22.5 degree angle, it will be 50% speed of light

In each seconds i sends a light pulse, so i drew it in 45 degree angle.

But the intersection of light pulse and speed of the object doesn't match with time in my graph

The first light pulse which i sent should intersect at t=2 in my graph but it intersect only below 2 second.

So if i try to adjust the graph inorder to reach at t=2 the angle changes and it will increase the speed of the object. This is like the same for all 4 light pulses

I know moving objects contract in length, but this isn't that

I also know time slows in moving object, but i don't need to care, i need my spacetime graph to be correct, they may receive it in different times

If it is my mistake help me to find it.

The picture is below

http://www.flickr.com/photos/sreenath666/10286909563/ [Broken]

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Spacetime diagram drawing problem

Tags:

**Physics Forums | Science Articles, Homework Help, Discussion**