[Faisal]

The value of Plank’s constant is 6.63 * 10^-34 J * s. The velocity of light is 3.0 * 10⁸ m * s-1. Which value is closest to the wave length in nanometers of a quantum of light with frequency of 8 * 10¹⁵ sec-1?
        A. 3 * 107
        B. 4 * 101
        C. 5 * 10-18
        D. 2 * 10-25
        E. 1 * 10-25
I used the formula wavelength=speed of light*frequency
so 3.0 * 10⁸ = wavelength* 8 * 10¹⁵ which gives wavelength as 3.75*10^-8...since the qustion ask for nanometres....therfore the answer is B...wrong!The answer is C....HOW???Can anyone plz tell me wht I am missing.Thank you

[DevaDevil]

hmm

I also arrive at 4 * 10¹ nm

[Faisal]

I think we hafta use the plank's constant somehow but the only equation I knw is E=hf..which doesn't have any use here..

[Borek]

37.5 nm, which is B for me as well.

[Faisal]

Must be something wrong with the question...

[cliverlong]

37.5 nm, which is B for me as well.

Agree.

Planck's constant is irrelevant to the problem as you have written it since lambda = c / frequency

Are you sure the answers provided in the original question are as you have written? (cleaning up sub-script and super script)

  A. 3 * 10⁷
  B. 4 * 10¹
  C. 5 * 10^-18
  D. 2 * 10^-25
   E. 1 * 10^-25

Regards

Clive

[Faisal]

Yeah I juz copy pasted the question...I am sure the answer shown is C.

[enahs]

C is not the correct answer. It happens, people make mistakes. Could just be an error when typing in the correct answer in the computer system. No big deal.