# Randomly emit of photon

1. Feb 29, 2008

### coke

hi, as we know, lamp emits light not continuously but in 'burst', which we may call wave packet or photon. my question is,
1. Is it emitted one photon by one photon with random time delay ?
2. it is said that the duration time of the photon from white light is about 10^-9 sec(nanosecond), does it mean that each photon lasts for 10^-9 sec ?
3. if the above two questions are both correct, then does it mean that 10^-9 sec late after the emission of the first photon, wait an unpredictable time later, another photon emitted ? then how about the first one ? where does it go ? die out ?

can anyone help ? thank you so much !

2. Feb 29, 2008

### Andy Resnick

In brief,

1) You can calculate the rate of photon production by energy- say 0.1 W of visible light is emitted from a bulb, assume 0.5 microns for a wavelength.

2) That's not correct- the 'coherence time' of broadband visible light can be around 1 ns. That is different from 'existence time'. Coherence means how predictable the field is in the future, given current knowledge of it- for broadband visible light, I can predict the value about 1 ns in advance.