SATHEE: Optics Question 125

Optics Question 125

Question: Two point light sources are 24 cm apart. Where should a convex lens of focal length 9 cm be put in between them from one source so that the images of both the sources are formed at the same place

Options:

A) 6 cm

B) 9 cm

C) 12 cm

D) 15 cm

Show Answer

Answer:

Correct Answer: A

Solution:

The given condition will be satisfied only if one source (S1) placed on one side such that u < f (i.e. it lies under the focus).

The other source (S2) is placed on the other side of the lens such that u > f (i.e. it lies beyond the focus).

If $S_{1}$ is the object for lens then $\frac{1}{f} = \frac{1}{- y} - \frac{1}{- x}$

$\Rightarrow$ $\frac{1}{y} = \frac{1}{x} - \frac{1}{f}$ …..(i) If $S_{2}$ is the object for lens then $\frac{1}{f} = \frac{1}{+ y} - \frac{1}{- (24 - x)}$

$\Rightarrow$ $\frac{1}{y} = \frac{1}{f} - \frac{1}{(24 - x)}$ …..(ii) From equation (i) and (ii) $\frac{1}{x} - \frac{1}{f} = \frac{1}{f} - \frac{1}{(24 - x)}$

$\Rightarrow$ $\frac{1}{x} + \frac{1}{(24 - x)} = \frac{2}{f} = \frac{2}{9}$

$\Rightarrow$ $x^{2} - 24 x + 108 = 0$ . After solving the equation $x = 18 c m$ , 6 cm.

Optics Question 125

Question: Two point light sources are 24 cm apart. Where should a convex lens of focal length 9 cm be put in between them from one source so that the images of both the sources are formed at the same place

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

Optics Question 125

Question: Two point light sources are 24 cm apart. Where should a convex lens of focal length 9 cm be put in between them from one source so that the images of both the sources are formed at the same place

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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