SATHEE: Optics Question 81

Optics Question 81

Question: A short linear object of length $l$ lies along the axis of a concave mirror of focal length f at a distance $u$ from the pole of the mirror. The size of the image is approximately equal to

[IIT-JEE 1988; BHU 2003; CPMT 2004]

Options:

A) $l {(\frac{u - f}{f})}^{1 / 2}$

B) $l {(\frac{u - f}{f})}^{2}$

C) $l {(\frac{f}{u - f})}^{1 / 2}$

D) $l {(\frac{f}{u - f})}^{2}$

Show Answer

Answer:

Correct Answer: D

Solution:

From mirror formula $\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$ …..(i)

Differentiating equation (i), we obtain $0 = - \frac{1}{v^{2}} d v - \frac{1}{u^{2}} d u$

$\Rightarrow d v = - {(\frac{v}{u})}^{2} d u$ …..(ii)

Also from equation (i) $\frac{v}{u} = \frac{f}{u - f}$ …..(iii)

From equation (ii) and (iii) we get $d v = - {(\frac{f}{u - f})}^{2} . l$

Therefore size of image is ${(\frac{f}{u - f})}^{2} l .$

Optics Question 81

Question: A short linear object of length $l$ lies along the axis of a concave mirror of focal length f at a distance $u$ from the pole of the mirror. The size of the image is approximately equal to

Options:

Answer:

Solution:

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Optics Question 81

Question: A short linear object of length l lies along the axis of a concave mirror of focal length f at a distance u from the pole of the mirror. The size of the image is approximately equal to

Options:

Answer:

Solution:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

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Question: A short linear object of length $l$ lies along the axis of a concave mirror of focal length f at a distance $u$ from the pole of the mirror. The size of the image is approximately equal to