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why does photoelectric emission occur only when there is a certain threshold frequency of incident radiation?

According to the particle theory of light, hf=φ+KEmax, so along with the minimum amount of energy required, there is a minimum frequency as well, φ= hf o . Thus, the incident photon must have a frequency hig...
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Answered by Nikolas P. • Physics tutor
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Calculate the pH of the solution formed when 30 cm3 of 0.150 moldm-3 aqueous sulfuric acid is added to 30 cm3 of 0.200 moldm-3 aqueous potassium hydroxide at 25 C.

H 2 SO 4 ---> 2H + + SO 4 2- KOH ---> OH - + K + Initial moles of Sulfuric acid: Volume x Concentration = Moles (30/1000) x 0.150 = 4.5x10 -3 mol Moles of H + made by sulfuric acid: It is a 1:2 ratio o...
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Answered by William D. • Chemistry tutor
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Compare the effect of imagery in any two poems by Seamus Heaney

Firstly, I would structure my essay in the style of compare and contrast , as this is what the examiners are ultimately looking for. Say I choose Death of a Naturalist and The Follower by Seamus Heaney. I’d ...
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How do I answer a source analysis question?

The first thing to remember when analysing a historical primary source is that it will always be of some value. Most primary source exam questions ask of a source's value, or of its use to a historian, and i...
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Answered by Sean H. • History tutor
10829 Views

How would I use the imperfect and pluperfect subjunctive in 'If Clauses'?

As A-level students, you will hear over and over again how you must have a variety of tenses - especially sophisticated ones - in your essays and your oral presentations in order to get to those top marks. O...
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Answered by Charlotte V. • Spanish tutor
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