Q&A - PSLE Science
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the answer should be ‘b’
it is impossible for ‘c’ to happen because it is impossible to retain the same brightness or to achieve reflection from infinite distance (the line plateauing means it is reflected from infinite distance, which is impossible).
the reflection must end at some distance because the further the light source is, the more the light will be dispersed along the way, hence eventually zero light reflected -
verykiasu2010:
thank u. anyways... the answer key says A. any explanation why?the answer should be 'b'
it is impossible for 'c' to happen because it is impossible to retain the same brightness or to achieve reflection from infinite distance (the line plateauing means it is reflected from infinite distance, which is impossible).
the reflection must end at some distance because the further the light source is, the more the light will be dispersed along the way, hence eventually zero light reflected -
I no science teacher but i think the question is incomplete unless the units of the x axis is given.
If one unit is 100m then B is best.
If one unit is 1000m then is A better as the cyclist need not be seen 4 km away.
If one unit is 10m then A or B will not be sufficient, 40 m will be too short to react. -
Robertpattinsonidle:
I think your teacher is correct
thank u. anyways... the answer key says A. any explanation why?verykiasu2010:
the answer should be 'b'
it is impossible for 'c' to happen because it is impossible to retain the same brightness or to achieve reflection from infinite distance (the line plateauing means it is reflected from infinite distance, which is impossible).
the reflection must end at some distance because the further the light source is, the more the light will be dispersed along the way, hence eventually zero light reflected
the one who gave the answer for the answer key probably read the graph but has the thinking process in the opposite, misinterpreted the info : shorter distance represented by the graph means the light stopped being reflected at that short distance - meaning it won't reflect anymore after that distance and hence not a good material for safety vest - which has to be as reflective as possible. the answer giver may be thought shorter distance needed to reflect light, hence is better. This is not the case
for 'b' it is able to have the light reflected at a longer distance, meaning more visible from longer distance than 'a', hence better material for safety vest.
p.s.
edited with more explanation -
Sun_2010:
no need distance in units lah, the length represented by 'a', 'b', 'c' are clearly different, so will not be mistaken in the diagramI no science teacher but i think the question is incomplete unless the units of the x axis is given.
If one unit is 100m then B is best.
If one unit is 1000m then is A better as the cyclist need not be seen 4 km away.
If one unit is 10m then A or B will not be sufficient, 40 m will be too short to react. -
verykiasu2010:
The question said A,B, C were plotted results, not imaginary.the answer should be 'b'
it is impossible for 'c' to happen because it is impossible to retain the same brightness or to achieve reflection from infinite distance (the line plateauing means it is reflected from infinite distance, which is impossible).
the reflection must end at some distance because the further the light source is, the more the light will be dispersed along the way, hence eventually zero light reflected
It was a trick question huh?
While I agree with you that it is not possible to obtain the same brightness over infinite distance,
for our understanding on examiners' expectations,
Are P6 students expected to analyse and draw a conclusion from the graphs
or are they expected to extrapolate beyond what's shown? -
Way2GO:
yes plotted, based on readings taken from the light sensor measuring the reflection. a good reflective material would be able to reflect the light over (or to) a longer distance, tio bo ?
The question said A,B, C were plotted results, not imaginary.verykiasu2010:
the answer should be 'b'
it is impossible for 'c' to happen because it is impossible to retain the same brightness or to achieve reflection from infinite distance (the line plateauing means it is reflected from infinite distance, which is impossible).
the reflection must end at some distance because the further the light source is, the more the light will be dispersed along the way, hence eventually zero light reflected
It was a trick question huh?
answer 'c' is just to trick and confuse, not unusual. it is an impossible material to have property to reflect an infinite distance -
verykiasu2010:
yes plotted, based on readings taken from the light sensor measuring the reflection. a good reflective material would be able to reflect the light over (or to) a longer distance, tio bo ?
The question said A,B, C were plotted results, not imaginary.Way2GO:
[quote=\"verykiasu2010\"]the answer should be 'b'
it is impossible for 'c' to happen because it is impossible to retain the same brightness or to achieve reflection from infinite distance (the line plateauing means it is reflected from infinite distance, which is impossible).
the reflection must end at some distance because the further the light source is, the more the light will be dispersed along the way, hence eventually zero light reflected
It was a trick question huh?
answer 'c' is just to trick and confuse, not unusual. it is an impossible material to have property to reflect an infinite distance[/quote]solli, please see my edited post.
you replied as I was editing. -
Way2GO:
reflective properties of materials is within the scope of PSLE science. No ?
The question said A,B, C were plotted results, not imaginary.verykiasu2010:
the answer should be 'b'
it is impossible for 'c' to happen because it is impossible to retain the same brightness or to achieve reflection from infinite distance (the line plateauing means it is reflected from infinite distance, which is impossible).
the reflection must end at some distance because the further the light source is, the more the light will be dispersed along the way, hence eventually zero light reflected
It was a trick question huh?
While I agree with you that it is not possible to obtain the same brightness over infinite distance,
for our understanding on examiners' expectations,
Are P6 students expected to analyse and draw a conclusion from the graphs
or are they expected to extrapolate beyond what's shown?
the question requires the student to draw conclusion. no need to extrapolate. they need to ask this : which one can reflect the longest distance? the red herring is the one with infinite distance -
verykiasu2010:
Thanks for explaining the question and your answer to us. Your assistance is very much appreciated. :thankyou:the answer should be 'b'
it is impossible for 'c' to happen because it is impossible to retain the same brightness or to achieve reflection from infinite distance (the line plateauing means it is reflected from infinite distance, which is impossible).
the reflection must end at some distance because the further the light source is, the more the light will be dispersed along the way, hence eventually zero light reflected
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