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 lens has radii of curvature of +20 cm and +30 cm . The material...
A lens has radii of curvature of and . The material of the lens has a refracting index of . Determine the focal length of the lens when it is placed in air.
Options
- A
- B
- C
- D
Correct answer
D.
Step-by-step solution
Using the Lens Maker's formula:
\left(\dfrac{1}{R_1} - \dfrac{1}{R_2}\right)
Given , , and .
Substituting the values:
\dfrac{1}{f} = (
\left(\dfrac{3 - 2}{60}\right)
\dfrac{1}{f} =\dfrac{1}{60}
\dfrac{1}{f} = \dfrac{1}{100}
\left(\dfrac{1}{R_1} - \dfrac{1}{R_2}\right)
Given , , and .
Substituting the values:
\dfrac{1}{f} = (
\left(\dfrac{3 - 2}{60}\right)
\dfrac{1}{f} =\dfrac{1}{60}
\dfrac{1}{f} = \dfrac{1}{100}