Q274 · Practice questionComplex unfamiliar5 marks
QUESTION 274 (5 marks)
In a photoelectric experiment the collector potential relative to the emitter at zero photocurrent is , where is the positive stopping-potential magnitude. A fitted graph of against frequency passes through and . Use .
a)[3 marks]
Use the fit to determine Planck extquotesingle s constant and the work function in eV.
b)[2 marks]
Determine the collector potential required to stop the most energetic electrons at .
WORKED SOLUTION
5 marksPractice marking scheme
ANSWER
(a) ; . (b) relative to the emitter.
Worked solution
(a) , so gradient and . The intercept is , giving or .
(b) The fitted stopping magnitude is . The collector must repel electrons, so .
Equivalent physically justified methods, alternative valid sketches and consistent units accepted.
Accept sensible significant figures and consistent rounding from stated constants.
Part a: Determine the fitted slope and use h = e times slope.
Part a: Obtain the intercept or equivalent energy balance.
Part a: Determine the work function in eV.
Part b: Evaluate the fitted stopping magnitude.
Part b: Give the negative collector potential with the stated reference.
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