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  • Time required for making a print at a distance of 40 cm from a 60 watt lamp is 12.8 second. If the distance is decreased to 25 cm, then time required in making the similar print will be<div cla

Time required for making a print at a distance of 40 cm from a 60 watt lamp is 12.8 second. If the distance is decreased to 25 cm, then time required in making the similar print will be

Option: 1

15 \mathrm{sec}


Option: 2

10 \mathrm{sec}


Option: 3

5 \mathrm{sec}


Option: 4

 remains some.


Answers (1)

best_answer

If prints are similar,
\mathrm{E_{1} t_{1}=E_{2} t_{2} \Rightarrow \frac{I_{1}}{r 1^{2}} t 1=\frac{I_{2}}{r 2^{2}} x t_{2}}
\mathrm{\text { But } I_{1}=I_{2} }

\mathrm{\therefore t_{2}=\frac{r 2^{2}}{r 1^{2}} x t_{1} \Rightarrow t_{2}=5 \mathrm{sec} }.

Posted by

Pankaj Sanodiya

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