Download App

Optical Instruments — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsOptical Instruments2 Marks
Question
A simple microscope is rated 5 for a normal relaxed eye. What will be its magnifying power for a relaxed farsighted eye whose near point is 40cm?
✓

Answer

The simple microscope has magnification of 5 for normal relaxed eye (D = 25cm).

Because, the eye is relaxed the image is formed at infinity (normal adjustment)

So, $\text{m}=5=\frac{\text{D}}{\text{f}}=\frac{25}{\text{f}}\Rightarrow\text{f}=5\text{cm}$

For the relaxed farsighted eye, $\text{D} = 40\text{cm}$

So, $\text{m}=\frac{\text{D}}{\text{f}}=\frac{40}{5}=8$

So, its magnifying power is 8X.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Short Answer Type Questions [2M]" from Optical Instruments→Optical Instruments — all question types→Physics STD 12 Science question papers→Bihar Board STD 12 Science question papers→Bihar Board question paper generator→

Similar questions

Can we measure the potential difference across an unbiased p–n junction by connecting a sensitive voltmeter across it?
→
The plates of a parallel-plate capacitor are made of circular discs of radii 5.0cm each. If the separation between the plates is 1.0mm, what is the capacitance?
→
Draw a labelled ray diagram to show image formation by a compound microscope and write the expression for its resolving power.
→
Verify that the units weber and volt-second are the same.
→
Electrons are emitted from the surface when green light is incident on it, but no electrons are ejected when yellow light is incident on it. Do you expect electrons to be ejected when surface is exposed to (i) Red light and (ii) Blue light?
→
Which of the following can act as a source of electromagnetic waves:
  1. A charge moving with a constant velocity.
  2. A charge moving in a circular orbit.
  3. A charge at rest.
Give reason.
→
If the resultant torque of all the forces acting on a body is zero about a point, is it necessary that it will be zero about any other point?
→
The distance between the two plates of a parallel plate capacitor is 4 mm . A 3 mm thick dielectric strip having dielectric constant 3 is placed between the plates parallel to the plates. The distance between the plates is arranged in such a way that the capacitance of the capacitor becomes $2 / 3$ of the initial capacitance. What is the new distance between the plates?
→
A metal rod of length ' $\ell$ ' is placed normal to a uniform magnetic field 'B' and moved with a constant linear speed 'v' perpendicular to the magnetic field. Then find the induced motional e.m.f. between its ends. Draw the necessary diagram.
→
A parallel plate capacitor with air between the plates has a capacitance of 8 pF. The separation between the plates is now reduced by half and the space between them is filled with a medium of dielectric constant 5. Calculate the value 
of capacitance of the capacitor in the second case.
→