Ray Optics And Optical Instruments

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A person uses + 1.5 D glasses to have normal vision from 25 cm onwards. He uses a + 20 D lens as a simple microscope to see an object. What is the maximum magnifying power if he uses the microscope without glasses.

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Solution

Let d be the distance of near point of the person without glasses.

Focal length of glasses

f₁ = $\frac{100}{P_{1}}$

= $\frac{100}{1.5}$

f₁ = $\frac{200}{3}$

Now u = $-$ 25 cm

v = ?

From lens formula

$\frac{1}{v} - \frac{1}{u} = \frac{1}{f_{1}}$

$\frac{1}{v} = \frac{1}{f_{1}} + \frac{1}{u}$

⇒ = $\frac{3}{200} - \frac{1}{25}$

⇒ $\frac{1}{v} = - \frac{5}{200}$

∴ v = $- \frac{200}{5}$

v = $-$ 40 cm

Therefore, the near point of the person is 40 cm.

Focal length of microscope,

f₂ = $\frac{100}{P_{2}}$

= $\frac{100}{20}$

f₂ = 5 cm

∴ M = 1 + $|\frac{d}{f_{2}}|$

M = 9

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Ray Optics And Optical Instruments

A person uses + 1.5 D glasses to have normal vision from 25 cm onwards. He uses a + 20 D lens as a simple microscope to see an object. What is the maximum magnifying power if he uses the microscope without glasses.

8

9

10

11

Some More Questions From Ray Optics and Optical Instruments Chapter

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For Daily Free Study Material Join wiredfaculty

Ray Optics And Optical Instruments

A person uses + 1.5 D glasses to have normal vision from 25 cm onwards. He uses a + 20 D lens as a simple microscope to see an object. What is the maximum magnifying power if he uses the microscope without glasses. 8 9 10 11

Some More Questions From Ray Optics and Optical Instruments Chapter

Two lenses of power -15D and +5D are in contact with each other. The focal length of the combination is

The angle of incidence at which reflected light totally polarized for reflection from air to glass (refractive index n), is

If θ1 and θ2 be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip θ is given by

A thin prism having refracting angle 10° is made of glass of refractive index 1.42. This prism is combined with another thin prism of a glass of refractive index 1.7. This combination produces dispersion without deviation. The refracting angle of second prism should be

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

A person uses + 1.5 D glasses to have normal vision from 25 cm onwards. He uses a + 20 D lens as a simple microscope to see an object. What is the maximum magnifying power if he uses the microscope without glasses.

8

9

10

11