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8 Cards in this Set
- Front
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When ultraviolet light of frequency 3. 0 × 1015 Hz is incident on the surface of a metal,electrons of maximum kinetic energy 1. 7 × 10–18 J are emitted. 4 (a) Explain why the emitted electrons have a range of kinetic energies up to a maximumvalue. |
The energy of the photon which gives the electron energy is fixed. the energy the electron receives has to overcome the work function. The maximum EK of an electron is the energy of the photon minus the work function. Deeper electrons require more energy to remove so will have a lower EK. |
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The photoelectric effect suggests that electromagnetic waves can exhibit particle - likebehaviour. Explain what is meant by threshold frequency and why the existence of athreshold frequency supports the particle nature of electromagnetic waves. |
The threshold frequency is the minimum frequency for the emission of electrons below it electrons wont be emitted as the energy of the photon is below the work function. wave theory cant explain this since the energy increases with intensity. therefore light travels as photons and it's energy is delivered in discrete packets known as photons and thus explains why electron is immediate. |
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Describe how the strong nuclear force between two nucleons varies with the separationof the nucleons quoting suitable values for separation |
repulsive then attractive ! short range (if distance quoted must be of order fm) ! 3correct distance for cross over (accept range 0.1 fm 1.0 fm) ! |
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What must be done to validate the predictions of an unconfirmed scientifictheory? |
hypothesis needs to be tested by experiment !experiment must be repeatable ! |
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Explain why the photoelectric effect is not observed below the thresholdfrequency. |
energy of a photon depends on the frequency below the threshold frequency it doesn't have enough energy to overcome the work function and liberate the electron. |
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Why do the excited mercury atoms emit photons of characteristic frequencies? |
Mercury atoms have specific energy levels when an electron changes energy electrons the lose a specific amount of energy in the form of a photon which, according to its energy, will have specific frequency. |
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Explain how the coating on the inside of a fluorescent tube emits visible light. |
It absorbs UV photons and emits photons of a lower frequency. |
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The student repeats the experiment with a battery of the same emf but negligibleinternal resistance. State and explain how you would now expect the power dissipatedin Y to vary as the resistance of Y is increased from 0.5 Ω to 6.5 Ω. cell-resistor |
Power would decrease as Resistance increases as the the resistor would receive all the emf of the battery due to no Internal resistance. due to P =V^2 /R so as R increases Power decreases |
