Some Help with these Questions Please (1 Viewer)

[wrxsti]

1) if a 2watt laser beam is emitting light of wavelength 600nm. the number of photons emitted from the laser beam per minute would be?


2) Explain how an Ac generator may be transformed into a Dc generator

3) Explain how the effects of Eddy Currents may be reduced (NOT heating effects)

Thanks

Physics is KILLING ME . its the only subject i have trouble with... ive memorised the course yet i can only do around 75% of HSC questions......
Hopefully you guys can help me with these questions

 

[xiao1985]

1) 600 nm laser:
c=f x lamda
f = c/lamda
f = 3e8 / 6e-7 = 1.8 e16

energy per photon = hf
energy per photon therefore = 6.626 e-34 x 1.8 e16 = 1.19268e-17 J/photon

now, 1watt = 1J/s

therefore 1/1.19268e-17 = 8.38e16 photons / s

2) Use a split ring commutator?! Or a rectifier?

3) laminating, use of poor electric conductors (say Fe)

 

[wrxsti]

Thanks Xia for helping me for the 1000th time

 

[xiao1985]

...

it's xiao =p

edit
oh btw, I found an error in my answer...
spot the error!!

 

[wrxsti]

lol..... mmmhmmm ill get back to you in a few hours... im revising this chapter fulli soon

 

[wrxsti]

i kno what you did wrong for your nanometers u did ^-7 when its supposed to be ^-9 is that the mistake ?

 

[xiao1985]

nah, 600 nm = 600x 10^-9 = 6.00 x 10^-7

it's silly though... question asks 2 watt, but in answer i used 1 watt :$