A lady uses +1.5D glasses to have normal vision from 25cm onwards. She uses a 20D lens as a simple microscope to see an object. Find the maximum magnifying power if she uses then microscope
- Together with her glass
- Without the glass. Do the answers suggest that an object can be more clearly seen through a microscope without using the correcting glasses?
Download our app for free and get started
The lady uses +1.5D glasses to have normal vision at 25cm.So, with the glasses, her least distance of clear vision = D = 25cm
Focal length of the glasses $=\frac{1}{1.5}\text{m}=\frac{100}{1.5}\text{cm}$
So, without the glasses her least distance of distinct vision should be more
If, $\text{u}=-25\text{cm},$
$\text{f}=\frac{100}{1.5}\text{cm}$
Now, $\frac{1}{\text{v}}-\frac{1}{\text{u}}=\frac{1}{\text{f}}=\frac{1.5}{100}-\frac{1}{25}=\frac{1.5{-4}}{100}=\frac{-2.5}{100}$
$\Rightarrow \text{v}=-40\text{cm}$ = near point without glasses
Focal length of magnifying glass $=\frac{1}{20}\text{m}=0.05\text{m}=5\text{cm}=\text{f}$
Focal length of the glasses $=\frac{1}{1.5}\text{m}=\frac{100}{1.5}\text{cm}$
So, without the glasses her least distance of distinct vision should be more
If, $\text{u}=-25\text{cm},$
$\text{f}=\frac{100}{1.5}\text{cm}$
Now, $\frac{1}{\text{v}}-\frac{1}{\text{u}}=\frac{1}{\text{f}}=\frac{1.5}{100}-\frac{1}{25}=\frac{1.5{-4}}{100}=\frac{-2.5}{100}$
$\Rightarrow \text{v}=-40\text{cm}$ = near point without glasses
Focal length of magnifying glass $=\frac{1}{20}\text{m}=0.05\text{m}=5\text{cm}=\text{f}$
- The maximum magnifying power with glasses
- Without the glasses, D = 40cm.
Download our appand get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
Similar Questions
- 1A hemispherical portion of the surface of a solid glass sphere $(\mu=1.5)$ of radius r is silvered to make the inner side reflecting. An object is placed on the axis of the hemisphere at a distance 3r from the centre of the sphere. The light from the object is refracted at the unsilvered part, then reflected from the silvered part and again refracted at the unsilvered part. Locate the final image formed.View Solution
- 2View Solution
- With the help of a suitable ray diagram, derive the mirror formula for a concave mirror.
- The near point of a hypermetropic person is 50 cm from the eye. What is the power of the lens required to enable the person to read clearly a book held at 25 cm from the eye?
- 3View SolutionIn many experimental set-ups the source and screen are fixed at a distance say D and the lens is movable. Show that there are two positions for the lens for which an image is formed on the screen. Find the distance between these points and the ratio of the image sizes for these two points.
- 4View SolutionA small bulb is placed at the bottom of a tank containing water to a depth of 80cm. What is the area of the surface of water through which light from the bulb can emerge out? Refractive index of water is 1.33. (Consider the bulb to be a point source).
- 5View Solution
- Draw a ray diagram to show refraction of a ray of monochromatic light passing through a glass prism.
- Explain briefly how the phenomenon of total internal reflection is used in fibre optics.
- 6View SolutionA diverging lens of focal length 20cm and a converging lens of focal length 30cm are placed 15cm apart with their principal axes coinciding. Where should an object be placed on the principal axis so that its image is formed at infinity?
- 7View SolutionA jar of height h is filled with a transparent liquid of refractive index μ (Fig). At the centre of the jar on the bottom surface is a dot. Find the minimum diameter of a disc, such that when placed on the top surface symmetrically about the centre, the dot is invisible.
- 8View SolutionA person with a normal near point (25 cm) using a compound microscope with objective of focal length 8.0 mm and an eyepiece of focal length 2.5 cm can bring an object placed at 9.0 mm from the objective in sharp focus. What is the separation between the two lenses? Calculate the magnifying power of the microscope.
- 9View SolutionA convex lens has a focal length of 10cm. Find the location and nature of the image if a point object is placed on the principal axis at a distance of:
- 9.8cm
- 10.2cm from the lens.
- 10View SolutionOne day Chetan’s mother developed a severe stomach ache all of a sudden. She was rushed to the doctor who suggested for an immediate endoscopy test and gave an estimate of expenditure for the same. Chetan immediately contacted his class teacher and shared the information with her. The class teacher arranged for the money and rushed to the hospital. On realising that Chetan belonged to a below average income group family, even the doctor offered concession for the test fee. The test was conducted successfully.
Answer the following questions based on the above information:- Which principle in optics is made use of in endoscopy?
- Briefly explain the values reflected in the action taken by the teacher.
- In what way do you appreciate the response of the doctor on the given situation?