January 2010- ocr physics g482

For 4aii, why don't u use the gradient of the curve at 1.7V instead of point values like u would for velocity
For question 7biii: Just what does it mean in the mark scheme when it says
photons absorbed by electrons without release?- isn't this impossible
recombination of ion pairs in insulaing layer
scattering of photons?
For 8ci, the examiners report says .This last section was a good discriminator with the better candidates correctly equating the electrical potential energy to the final kinetic energy of the electron. A common misconception was to use the de Broglie wavelength and the energy expression for a photon instead.
Why couldn't u do this
For question 8cii,
Basically what does the second sentence of the mark scheme mean?- they will be attracted back if the cathode is positive- well the cathode is always negative right? the cathode cannot be positive.
See mark scheme and paper attached in reply