Speed inorder to shift green light to blue light?

[Moviemann345]

Hypothetically if your in a jet or spaceship & are shining a green laser pen out the window how fast must you travel to cause the green light (570 nm) to change into low energy blue light (475 nm)

 

[Doc Al]

Look up the Doppler effect.

 

[Moviemann345]

fo = fv/(v ± vs)? This isn't a homework problem & I am not in a physics class, I was just curious

 

[Doc Al]

fo = fv/(v ± vs)? This isn't a homework problem & I am not in a physics class, I was just curious

You need to use the relativistic Doppler formula:

$$f_o = f_s \sqrt{\frac{1 + \beta}{1 - \beta}}$$

where β = v/c

Solve for β, then you'll have the speed. To convert wavelength to frequency, use c = fλ.

This tells you the frequency shift seen by an observer when the light source moves toward him at speed v.

 

[Moviemann345]

Oh ok thanks I'll try it out