Another photon energy question (1 Viewer)

[biscuit]

Jacaranda - page 206:
q11
A red laser emitting 600nm (wavelength = 6.0 x 10^-7 m) wavelength light and a blue laser emitting 450nm light emit the same power. Compare their rate of emitting photons.

the worked solution is here http://www.jaconline.com.au/physicsnsw/downloads/hsc/2005-02-fws-ch11.pdf

however, i don't get how they have done it..
can someone explain how to approach these q's?
thanks

 

[lollee]

ok i swear i neva did this sort of thing in class i am soo screwed

 

[helper]

1. Calculate the frequency of light c=frequency x wavelength
2. Calculate the amount of energy in a single photon E=hf
3. Calculate the Energy required. E=Pt
4. Calculate the number of photons Total Energy/Energy of one photon.


In the question above, they told you it was the same poswer. They assumed the power was 1W for 1 second.

 

[biscuit]

thanks man

 

[Wakaveli]

A quick way:

Rhf = BhF
R/B = hF/hf (F - blue frequency; f - red frequency) [let f=c/w]
R/B = w/W (W - blue wavelength; w- red wavlength)
R/B = 600/450
= 4/3 (1.333...)