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\begin{array}{l}{\text { An empty spherical flask of diameter } 15 \mathrm{cm} \text { is placed in water }} \\ {\text { of refractive index } 4 / 3 \text { . A parallel ray of light strikes the flask. }} \\ {\text { Where does it get focused, if observed from within the flask }} \\ {\text {,when measured from the center of the surface of spherical flask surface i.e., pole in cm }}\end{array}

Option: 1

22.5 


Option: 2

24.5


Option: 3

\infty


Option: 4

7.5 cm


Answers (1)

best_answer

 

 

The spherical flask placed inside water and a parallel beam of light striking on flask. The observer is observing from inside the flask.

\begin{array}{l}{\text { Using, } \frac{\mu_{2}}{v}-\frac{\mu_{1}}{u}=\frac{\left(\mu_{2}-\mu_{1}\right)}{R}} \\ {\text { Here, } u=-\infty, R=+\frac{15}{2} \mathrm{cm}, \mu_{1}=1 \text { and } \mu_{2}=\frac{4}{3}} \\ {\quad \frac{4 / 3}{v}-\frac{1}{(-\infty)}=\frac{(4 / 3-1)}{(+15 / 2)} \Rightarrow v=-\frac{45}{2} \mathrm{cm}=-22.5 \mathrm{cm}}\end{array}

As v is negative, the image will be formed on the same side as that of the object i.e. the side from which the parallel of light is incident on the flask. As shown in the figure, the parallel beam of light will appear to come from point I (virtual image)

 

Posted by

shivangi.bhatnagar

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