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Question 18M.3.SL.TZ2.a

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Date May 2018 Marks available [Maximum mark: 1] Reference code 18M.3.SL.TZ2.a
Level SL Paper 3 Time zone TZ2
Command term Show that Question number a Adapted from N/A
a.
[Maximum mark: 1]
18M.3.SL.TZ2.a

A student carries out an experiment to determine the variation of intensity of the light with distance from a point light source. The light source is at the centre of a transparent spherical cover of radius C. The student measures the distance x from the surface of the cover to a sensor that measures the intensity I of the light.

M18/4/PHYSI/SP3/ENG/TZ2/02

The light source emits radiation with a constant power P and all of this radiation is transmitted through the cover. The relationship between I and x is given by

I = P 4 π ( C + x ) 2

This relationship can also be written as follows.

1 I = K x + K C

Show that  K = 2 π P .

[1]

Markscheme

combines the two equations to obtain result

 

«for example  1 I = K2(C + x)2 =  4 π P (C + x)2»

OR

reverse engineered solution – substitute K =  2 π P  into 1 I = K2(C + x)2 to get I =  P 4 π ( C + x ) 2

 

There are many ways to answer the question, look for a combination of two equations to obtain the third one

[1 mark]

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