# relativity help (1 Viewer)

#### sssona09

##### Member
heey wondering what values I should use for T_0 and T_v to get the answer? how do I do this?

A space ship travelling at 0.75c sends a microwave message to earth. Calculate the speed of the transmission relative to earth if the spaceship was travelling
(a) away from earth
(b) calculate its speed relative to the spaceship in each case

a) 3 x 10^8 m/s
b) 3 x 10^8 m/s in each case

#### sida1049

##### Well-Known Member
The answer to both parts is the speed of light. Because the speed of light (i.e. EMR) is constant in every frame of reference, and microwave is an EMR. No calculation is actually required.

#### Sp3ctre

##### Active Member
You don't need to, the velocity of all electromagnetic waves will be 3x10^8 regardless, since microwaves are a type of EMW the answers to both parts are basically the speed of light, doesn't matter which direction the spaceship is travelling or what it's relative to

#### sssona09

##### Member
ohhh thank you guys

#### impulsebro89

##### New Member
Yeah just be careful with these type of trick questions. Always remember that the speed of light is constant in EVERY frame of reference, regardless of the motion of the observer. If you look at question 6 in the 2016 hsc physics paper, the question is kind of similar to this one.

#### YeetusMaximus

##### New Member
For future questions regarding dilation, you can take the value with subscript 0 as when the object is not moving and subscript v as when it is

#### fysiqs

##### New Member
its not a trick question.

Its just about knowing the absolutely most basic tenet of relativity.