• QCE

  • Urgent External Exam Questions

God
Unless we use numeric solver on our Graphics calcs

-jinx_58

    jinx_58
    Hey jinx_58,

    For the blackbody radiation question, you just use Wien's displacement formula which is λmax=b/T (where b=2.898x10-3). So, the answer should be T=257600K (I could be wrong tho).

    As for stopping voltage, I don't think you actually need to know that for U3&4 (hence, why its not seen in the syllabus) but I believe you would use this formula: eV0= hc/λ - W to work it out.

    Hope that helped.

    • PP

        PhytoPlankton
        Thank you PhytoPlankton.

        However, for question 8, the QCAA answers state it was Answer C, 190m. But for paper 2, QCAA has the wrong numbers subbed in for Question 9 so it could be a QCAA mistake.

        Thanks again,
        -jinx_58

            jinx_58
            I could be wrong but I just checked the marking guide and it says its answer A for question 8 in P1 multiple choice. Let me know if I just read that wrong.

            • PP

                PhytoPlankton
                Lol I can't read haha. Sorry about that 😅

                Also, are we supposed to know the wavelength of waves on the electromagnetic spectrum?

                -jinx_58

                    jinx_58
                    Haha that's all good.

                    As far as I know, I don't think you need to know the wavelength of waves on the EM spectrum. If they ask you for something like that, they should give you the spectrum or that information.

                    • PP

                      Howdy (again)

                      I did question 19 on the 2021 Paper 1 (multi-choice) and I got A. The answers however say its B. I feel like I did it wrong but the length given is the length at rest, which L_0. You would get B as the answer if you let L (contracted length) equal 125. Moreover, doesn't the length measured by an observer at rest need to be greater than someone in a moving reference frame?

                      Please correct me if I'm wrong and I messed up reading the question.

                      Edit: Could someone also please show the working out for Q13, 8, and 4

                      Link to the paper is below:
                      https://www.qcaa.qld.edu.au/downloads/senior-qce/sciences/snr_physics_21_ea_p1_mc_question.pdf

                      Thank you,
                      -jinx_58

                        jinx_58
                        Hello again jinx_58,

                        So L0 is the proper length which is the length at rest which is also the length measured by the moving observer (person on the spaceship) because to the observer on the spaceship, the spaceship is at rest (just like when you're in a car). L is the contracted length which is 125m because the stationary observer will see it moving at 0.3c and thus, the length will contract for them. You can watch this Crash Course video which explains length contraction: https://www.youtube.com/watch?v=AInCqm5nCzw.

                        Hope that helps!

                        • PP
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