# E according to the wavelength and frequency are

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e) According to, the wavelength and frequency are inversely proportional. Increasing thewavelength will cause a decrease in the frequency of the light. If this drops below thethreshold frequency, no photoelectrons will be emitted.
STAWA12T002 | Exploring Physics | Year 12 worked solutions | Revolutions in modern physics Set 12 to Set 15© Department of Education WA 20167f) If the frequency is above the threshold frequency, a higher intensity will increase thephotoelectron current. If the frequency is below the threshold frequency, no current will flow,and changing the intensity will not change this.g) If the surface of the metal is covered (and the material is opaque) light will not be able tostrike the surface of the metal. If this is the case, the photoelectric effect will not be seen.6.a)JeVNo solution as the incident energy is below the work function.b) No effect. The stopping potential is related to the maximum kinetic energy of the electronsthat are liberated. Doubling the intensity changes the amount of photoelectrons which areliberated, but not the energy of those electrons (this is related to increasing the frequency ofthe light). Therefore, there is no effect on the stopping potential.7.a) At the threshold frequency, electrons are free but have no kinetic energy.JeVb)mc)JeVd)eV
STAWA12T002 | Exploring Physics | Year 12 worked solutions | Revolutions in modern physics Set 12 to Set 15© Department of Education WA 20168e)eV =Jm.s-18.a)JeVeVeVb)eVJm.s-19.a) In order for photoelectrons to be emitted from the surface the photons must have aminimum energy to dislodge them. As E=hf, this corresponds to photons of a minimumfrequency. This is different for each material, however. 465nm light must correspond to afrequency which is higher than the threshold frequency in sodium, but not in platinum.b) The current will increase in sodium as a higher intensity will mean more photons areproduced, meaning more electrons will be liberated. As the light is below the thresholdfrequency for platinum, platinum’s current will remain at zero.c): increasing wavelength greatly greatly deceases frequency. Sodium will most likelystop producing electrons as a great decrease to frequency would put it below the thresholdfrequency, and platinum’s current will remain at zero.d): decreasing wavelength greatly increases frequency. Sodium will continue producingelectrons at the same rate, and platinum is likely to produce a photoelectron current as a greatincrease to its frequency will most likely bring it above the threshold frequency.e) Current will decrease in sodium, as a small reverse voltage will stop electrons with lowerkinetic energy from moving.
STAWA12T002 | Exploring Physics | Year 12 worked solutions | Revolutions in modern physics Set 12 to Set 15© Department of Education WA 2016910.a)Hzb)Jc)Jd)m11.There is no energy change, but there will be a decrease in the number of photoelectrons (adecrease in the current). The light source does not change in frequency so the energy of thephotons is constant throughout the entire process. The smoke, however, would cause photonto deflect from their path towards the photocell. This means less photons would interact withthe electrons on the surface of the photocell, causing less photoelectrons to be emitted. Thismeans the current would decrease.

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Term
Winter
Professor
Ms. Nilsson
Tags
Department of Education WA