Radiation from cesium-133 atom

[Ice-cream]

This is a question where i have absolutely NO idea where to start:

 

How long does it take for radiation from a cesium-133 atom to complete 1 million cycles? (ans: 1.087828 x 10^-4s)

 

Also another question:

Your friend holds a ruler by one end, letting the other end hang vertically. At the lower end, you hold your thumb and index finger on either side of the ruler, ready to grip it. Your friend releases the ruler without warning. You catch it as quickly as u can. if you catch the ruler 5.2cm from the lower end, what is your reaction time? (ans: 0.1s)

 

(I can't seem to gather enough info from the question except for distance = 5.2cm and g = 9.8m/s...)

 

Can anyone help me? thanx

[YT2095]

with the question about the rule, not only do you have to factor the rate of fall in m/sec^2 but also the distance between your thumb and forefinger.

if we take an extreme example, imagine you have yours arms open wide and you have to catch it with a clapping action, your reaction time may be the same, but the distance you have to travel over will probably see the rule hit the floor 1`st

[swansont]

This is a question where i have absolutely NO idea where to start:

 

How long does it take for radiation from a cesium-133 atom to complete 1 million cycles? (ans: 1.087828 x 10^-4s)

 

Cs-133 oscillates at 9192631770 Hz*, so the radiation oscillates at that frequency as well. The period (or time for one cycle) is the inverse of the frequency.

 

*unperturbed atom - no magnetic fields that would cause a Zeeman shift, of other radiation fields that would cause an AC Stark shift, etc. This is how the second is currently defined. Aren't you glad an atomic-clock guy answered this? I feel like I'm at work!

[Johnny5]

no magnetic fields that would cause a Zeeman shift' date=' of other radiation fields that would cause an AC Stark shift, etc.

 

[/quote']

 

What is an AC Stark shift?

[swansont]

What is an AC Stark shift?

 

The Stark shift is from an electric field. It's called an AC shift if the field is oscillating, as in EM radiation. Cesium has a significant shift from ~10 micron radiation, which is what is emitted by room-temperature objects. Quantifying the amount of the shift can be problematic, and the answer affects how you think your atomic clock's output needs to be corrected to reflect precise time. It's only important for really precise time, however.