You are in a stationary space station when you notice your friend flies by in a

Question

You are in a stationary space station when you notice your friend flies by in a spaceship going a large fraction of the speed of light. A) You notice that it takes 4 seconds on your clock for a clock on his spaceship to indicate the passage of one second. If he measured his spaceship to be 240 m in length, how long would you measure his spaceship to be (along the direction he is moving)? B) How fast is his spaceship going with respect to your space station? An electron in a Lithium atom falls from the n = 4 state to the n = 3 state, giving off a photon of light. A) How much energy (eV) does the photon carry off? B) What is the frequency (Hz) of the photon? C) What is the wavelength (nm) of the photon? D) Is the photon visible? What color is it if so?

Explanation / Answer

8. (A) Y = 4

L = Y L0 = 4 x 240 = 960 m

(B) Y = 1 / sqrt[1 - (v/c)^2]

1 - (v/c)^2 = ( 1 / 4)^2 = 0.0625

v = 0.968 c

9. (A) E = 13.6 [ 1/3^2 - 1/4^2]

E = 0.66 eV

(b) E = h f

f = (0.66 x 1.6 x 10^-19) / (6.626 x 10^-34)

f = 1.60 x 10^14 Hz

(c) lambda = c / f = 1879 x 10^-9m

= 1879 nm

No, it is not in visibe region.

10. lamdba = 2 pi r = 3.324 x 10^-10 m

lambda = h / p

3.324 x 10^-10 = (6.626 x 10^-34) / (9.11 x 10^-31 x v)

v = 2.19 x 10^6 m/s

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