Gray | Photons hit Electrons

First day in the lab after some lengthy Christmas holidays! Almost a little bit too much. A proper way of starting the day means sharing a cup of coffee with my fellow lab rats. I love morning espressos in my favorite cup, hijacked virtuously from my previous job by means of polite mooching, yippie. 🙂

A double espresso in a huge cup.

Long time no espresso for me meant burning my tongue at the first sip, and hence this post. Can the “invested” thermal energy in a double espresso kill me if it was to be transformed into gamma rays? I offer you here some of my ultra-primitive (8th grader’s) random morning nonsense thoughts.

We can assume that coffee is water (oh what an irony) and therefore its specific heat would be 1.0 cal/g.degC i.e. same as water.
Because something annoys me with the unit of calories, let’s convert it to something more useful as e.g. jouls:

$1 cal = 4.184 J$

The volume of a double espresso equals the volume of two single espressos (WOW!) which therefore is 60 ml, let’s also assume that 60 ml of coffee weighs 60 g to make our life simpler.
Tap water is 20 deg C and a properly extracted espresso should be around 75 deg C, thus we have a delta of 55 deg C to “invest” in it. The energy required to get this precious liquid will be:

$55 \textdegree C \times 60 g \times 4,184 J = 13807,2 J$

Gray (Gy) is unit measuring the absorbed by a body ionising radiation which is defined as:

$1 Gy = 1 \frac{m^{2}}{s^{2}} = 1 \frac{J}{kg}$

We can thus very easily convert the energy required for heating the coffee to an absorbed radiation dose which would be:

$\frac{13807,2 J}{70 kg} = 187 Gy$

I use 70kg here as that’s the closest to an average person’s weight. So how much is 197 Gy? According to this wikipedia table, and assuming a 100% absorption rate 197 Gy would pretty much kill me within 24 hours. This is of course provided that we have 100% absorption rate. Other more accurate absorption models exist however, I’ll skip this for the time when humanity discovers what exactly black holes are…

If all my simple thoughts above are correct this happens to be a fairly scary fact. Hmmmm, another less deadly question pops-up to my mind. Can the very same energy kill a microchip if it is in the form of a focused (0.1mm) laser beam with 600nm wavelength projected onto the surface of a silicon die with Al top metal layer thickness of 8000 Å and assuming no passivation layer has been deposited on top???