Ascientist is studying the light emitted by several celestial objects. he records the shifts in each object’s spectral lines (in nm). based on these measurements, determine whether each object is moving toward or away from earth. use the diagram of the visible light spectrum to you. 400 nm shifted to 430 nm 610 nm shifted to 580 nm 512 nm shifted to 480 nm 670 nm shifted to 690 nm

-- 400 nm shifted to 430 nm . . . longer than it should be; "red shifted"; moving away from Earth  

-- 610 nm shifted to 580 nm . . . shorter than at source; "blue shifted"; moving toward Earth

-- 512 nm shifted to 480 nm . . . shorter than at source; moving toward Earth

-- 670 nm shifted to 690 nm . . .longer than at source; moving away from Earth

Now I'd just like to ask one more itty bitty question, that you can think about while you're on this subject:  Astronomers really do this.  They measure how much the wavelength CHANGED, from the time it left the original source until the time they detect it. But HOW do they know what the wavelength WAS when it left the source ? ? ?

THIS is the part that blows my mind !

Although your question is incomplete a general answer have been provided and they are :

When the spectral line shifts from 400nm to 430 nm it indicates that the object is moving away from the earth

When the spectral line shifts from 610 nm to 580 nm the object moves toward the Earth

When the spectral line shifts from 512nm to 480 nm the object moves toward the earth

when the spectral line shifts from 670 to 690 nm the object moves away from the earth.

The shift in spectral lines in each Objects indicates that celestial objects moves either towards the earth or away from the earth. when the spectral lines shifts from a lower value to a higher value the object moves toward the earth and the wavelength is longer at the source. while if the spectral lines shifts from a higher value to a lower value the objects moves away from the earth and the wavelength is shorter at the source

Hence with the help of visible light spectrum the shift from a lower spectral line value to a higher values indicates movement away from the earth and vice versa.

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a and b sometimes have a positive value