Asked by emily

Red light with a wavelength of 7.0x10^-7 m travels at a speed of c. When it enters glass it's speed is reduced to 2.0x10^8 m/s. Calculate the wavelength of this redlight in glass. Assume that the frequency does not change.

I'm really confused and I'm not sure how to do this question. Thank you!
Answered by emily
Ohh wait never mind.
Would it be
TIME = 7.0x10^-7 m / 2.0x10^8 m/s
=35s

And then you would plug it in as f=1/35s?
Answered by Steve
watch the units

wavelength(m) = speed(m/s) / frequency(1/s)
Answered by emily
I don't understand. So is the 35s part not right?

Because then you could plug it into the f=1/t formula.
Answered by bobpursley
It should be 0.35 seconds, shouldn't it?
Answered by emily
Oh wait I see, so then do you use the v=fx so solve for the frequency?

Like
2.0x10^8 m/s = 7.0x10^-7 m f

And then use that frequency to find the new wavelength?
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