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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Geometrical Optics

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Geometrical Optics

A concave mirror with a radius of curvature of 40 cm is positioned...

A concave mirror with a radius of curvature of 40 cm40 \text{ cm} is positioned in front of an illuminated point source at a distance of 30 cm30 \text{ cm} from it. Determine the location of the image.

Options

  1. A60 cm60 \text{ cm} from the mirror on the side of the object
  2. B60 cm60 \text{ cm} from the mirror on the opposite side of the object
  3. C120 cm120 \text{ cm} from the mirror on the opposite side of the object
  4. D12 cm12 \text{ cm} from the mirror on the side of the object

Correct answer

A. 60 cm60 \text{ cm} from the mirror on the side of the object

Step-by-step solution

Given, radius of curvature of the concave mirror, R=−40 cmR = -40 \text{ cm}

Focal length, f=R2=−20 cmf = \dfrac{R}{2} = -20 \text{ cm}

Object distance, u=−30 cmu = -30 \text{ cm}

Using the mirror formula:

1v+1u=1f\dfrac{1}{v} + \dfrac{1}{u} = \dfrac{1}{f}

1v+1−30=1−20\dfrac{1}{v} + \dfrac{1}{-30} = \dfrac{1}{-20}

1v=130−120\dfrac{1}{v} = \dfrac{1}{30} - \dfrac{1}{20}

1v=2−360=−160\dfrac{1}{v} = \dfrac{2 - 3}{60} = -\dfrac{1}{60}

v=−60 cmv = -60 \text{ cm}

The negative sign indicates that the image is formed in front of the mirror, which is on the same side as the object. Therefore, the image is located 60 cm60 \text{ cm} from the mirror on the side of the object.
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