A convex lens ' $A$ ' of focal length $20\mathrm{c}\mathrm{m}$ and a concave lens ' $\mathrm{B}$ ' of focal length $5\mathrm{c}\mathrm{m}$ are kept along the same axis with a distance ' $d$ ' between them. If a parallel beam of light falling on ' $A$ ' leaves ' $B$ ' as a parallel beam, then the distance ' $\mathrm{d}$ ' in $\mathrm{c}\mathrm{m}$  will be:

Correct Option - 2


Detailed Solution:

$\mathrm{d}={\mathrm{f}}_1-{\mathrm{f}}_2$

$=20-5$

$=15\mathrm{c}\mathrm{m}$

(1)

$\mathrm{q}=\mathrm{C}\mathrm{V}$

$\frac{\mathrm{d}\mathrm{q}}{\mathrm{d}\mathrm{t}}=\frac{\mathrm{C}\mathrm{d}\mathrm{V}}{\mathrm{d}\mathrm{t}}$

$I_d=C\left(V_0\omega \mathrm{c}\mathrm{o}\mathrm{s}?\omega t\right)$

$={\mathrm{V}}_0\omega \mathrm{C}\mathrm{o}\mathrm{s}\omega \mathrm{t}$

<div><div><picture><source srcset="" media=" (max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/1756977627phplkBODA.jpeg" alt="" width="430" height="286" loading="lazy"></picture></div><div><span contenteditable="false"> <math> <mi mathvariant="normal">d</mi> <mo>=</mo> <msub> <mrow> <mrow> <mi mathvariant="normal">f</mi> </mrow> </mrow> <mrow> <mrow> <mn>1</mn> </mrow> </mrow> </msub> <mo>-</mo> <msub> <mrow> <mrow> <mi mathvariant="normal">f</mi> </mrow> </mrow> <mrow> <mrow> <mn>2</mn> </mrow> </mrow> </msub> </math> </span></div><div><span contenteditable="false"> <math> <mo>=</mo> <mn>20</mn> <mo>-</mo> <mn>5</mn> </math> </span></div><div><span contenteditable="false"> <math> <mo>=</mo> <mn>15</mn> <mtext> </mtext> <mi mathvariant="normal">c</mi> <mi mathvariant="normal">m</mi> </math> </span></div><div> (1)</div><div><span contenteditable="false"> <math> <mi mathvariant="normal">q</mi> <mo>=</mo> <mi mathvariant="normal">C</mi> <mi mathvariant="normal">V</mi> </math> </span></div><div><span contenteditable="false"> <math> <mfrac> <mrow> <mrow> <mi mathvariant="normal">d</mi> <mi mathvariant="normal">q</mi> </mrow> </mrow> <mrow> <mrow> <mi mathvariant="normal">d</mi> <mi mathvariant="normal">t</mi> </mrow> </mrow> </mfrac> <mo>=</mo> <mfrac> <mrow> <mrow> <mi mathvariant="normal">C</mi> <mi mathvariant="normal">d</mi> <mi mathvariant="normal">V</mi> </mrow> </mrow> <mrow> <mrow> <mi mathvariant="normal">d</mi> <mi mathvariant="normal">t</mi> </mrow> </mrow> </mfrac> </math> </span></div><div><span contenteditable="false"> <math> <msub> <mrow> <mrow> <mi>I</mi> </mrow> </mrow> <mrow> <mrow> <mi>d</mi> </mrow> </mrow> </msub> <mo>=</mo> <mi>C</mi> <mfenced separators="|"> <mrow> <mrow> <msub> <mrow> <mrow> <mi>V</mi> </mrow> </mrow> <mrow> <mrow> <mn>0</mn> </mrow> </mrow> </msub> <mi>ω</mi> <mi mathvariant="normal">c</mi> <mi mathvariant="normal">o</mi> <mi mathvariant="normal">s</mi> <mo>? </mo> <mi>ω</mi> <mi>t</mi> </mrow> </mrow> </mfenced> </math> </span></div><div><span contenteditable="false"> <math> <mo>=</mo> <msub> <mrow> <mrow> <mi mathvariant="normal">V</mi> </mrow> </mrow> <mrow> <mrow> <mn>0</mn> </mrow> </mrow> </msub> <mi>ω</mi> <mi mathvariant="normal">C</mi> <mi mathvariant="normal">o</mi> <mi mathvariant="normal">s</mi> <mi>ω</mi> <mi mathvariant="normal">t</mi> </math> </span></div></div>

0 Upvotes 0 Upvotes 0 Downvotes

• • Report Abuse
• Comment