uth-1.amazonaws.com/pyq-question-images/batch-001/eb29b0f8d9d6.webp" loading="lazy" style="max-width:100%;height:auto;display:block;margin:0 auto;max-height:40vh;vertical-align:baseline" alt="JEE Main 2025 (Online) 22nd January Morning Shift Physics - Geometrical Optics Question 71 English Explanation">

We know, for a combination of a lens and a mirror,

$${P_{comb}} = 2{P_l} + {P_m}$$ ...... (1)

Also using lens maker formula,

$${1 \over {{f_l}}} = (\mu - 1)\left( {{1 \over R} - {1 \over { - R}}} \right) = (\mu - 1){2 \over R}$$

So using eq. (i),

$$ - {1 \over {{f_{comb}}}} = 2\left( {{1 \over {{f_l}}}} \right) - {1 \over {{f_m}}}$$

$$ \Rightarrow - {1 \over {{f_{comb}}}} = {{4(\mu - 1)} \over R} - {1 \over {\left( { - {R \over 2}} \right)}}$$

$$ \Rightarrow - {1 \over {{f_{comb}}}} = {{4(\mu - 1)} \over R} + {2 \over R}$$

$$ \Rightarrow - {1 \over {{f_{comb}}}} = {2 \over R}(2\mu - 2 + 1) = {2 \over R}(2\mu - 1)$$

$$ \Rightarrow {f_{comb}} = {{ - R} \over {2(2\mu - 1)}}$$

$$ \Rightarrow {R_{comb}} = 2{f_{comb}} = {{ - 2R} \over { - 2(2\mu - 1)}} = {{ - R} \over {2\mu - 1}}$$

Hence, distance $$ = {R \over {2\mu - 1}}$$

19:T659,

JEE Main 2025 (Online) 22nd January Morning Shift Physics - Geometrical Optics Question 71 Hindi Explanation

हम जानते हैं, लेंस और दर्पण के संयोजन के लिए,

$${P_{comb}} = 2{P_l} + {P_m}$$ ...... (1)

साथ ही लेंस निर्माता सूत्र का उपयोग करते हुए,

$${1 \over {{f_l}}} = (\

Geometrical Optics

Continue this paper

Similar Geometrical Optics PYQs

More practice from this question