How Much Energy is Carried by One Trillion Photons of 20 cm Microwaves?

[05holtel]

Homework Statement

GSM networks use microwaves of 20 cm in wavelength.

The energy carried by one trillion (10^12) photons of this wavelength is closest to ...
Question 1 answers
A)10-16 Joules
b)10-15 Joules
c)10-14 Joules
d)10-13 Joules
e)10-12 Joules

Homework Equations

Instructions: The speed of light is c = 3 x 108 m/s

Plank's constant is h = 6.63 x 10-34 J s

The Attempt at a Solution

E = hf

c = wavelength x f
f = (3.00 x 10^8) / (0.2) = 1.5E9
E = 6.63 x 10-34 J s x 1.5E9
E = 9.945E-25

Do I Multiply by 10^12 to account for the energy carried by one trillion (10^12) photons making the answer 9.945E-13 of d from above

 

[ehild]

Well, 9.945 is quite close to 10 isn't it? So 9.945E-13 is almost 10E-13 = 10^-12
The data given in the problem are written is a strange format, they mean 10^-12 (e), 10^-13 (d), and so on.


ehild

 

[05holtel]

I thought 9.945^-13 is equivalent to 10^-13. So I do not understand why 10^-12 is the answer

 

[ehild]

You got the energy 9.945E-13. It is not the same as 9.945^-13.

"E-13" stands for 10^-13. 9.945E-13 means 9.945 multiplied by 10^-13 .

ehild