English
Maharashtra State BoardSSC (English Medium) 10th Standard

Write scientific reason. Adults need bifocal lens spectacle.

Advertisements
Advertisements

Question

Write scientific reason.

Adults need bifocal lens spectacle.

Explain
Short/Brief Note
Advertisements

Solution

  1. The ability of the ciliary muscles near the eye lens to change the focal length of the lens decreases with age.
  2. As a result, sometimes adults suffer from both nearsightedness and farsightedness.
    Therefore, adults need bifocal lens spectacle.
shaalaa.com
  Is there an error in this question or solution?
Chapter 7: Lenses - Write scientific reasons [Page 24]

APPEARS IN

RELATED QUESTIONS

(a) Draw a ray diagram to show the formation of an image by a convex lens when an object is placed in front of the lens between its optical centre and principal focus.

(b) In the above ray diagram, mark the object distance (u) and the image distance (v) with their proper signs (+ve or –ve as per the new Cartesian sign convention) and state how these distances are related to the focal length (f) of the convex lens in this case.

(c) Find the power of a convex lens which forms a real and inverted image of magnification –1 of an object placed at a distance of 20 cm from its optical centre.


A student has obtained a magnified image of a flame on a screen using a convex lens. To draw the corresponding ray diagram to show the image formation, which of the following two rays whose paths after refraction are shown, should he select ?

(A) I and II

(B) II and III

(C) III and IV

(D) I and III


Where should an object be placed in order to use a convex lens as a magnifying glass? 


If an object is at a considerable distance (or infinity) in front of a convex lens, where is the image formed?


What type of lens would you use as a magnifying glass? How close  must the object be to the lens?


Describe with the help of a ray diagram the nature, size and position of the image formed when an object is placed in front of a convex lens between focus and optical centre. State three characteristics of the image formed.


With the help of a labelled diagram explain how a convex lens converges a beam of parallel light rays. Mark the principal axis, optical centre, principal focus and focal length of the convex lens on the diagram. 


A convex lens has a focal length of 10 cm. At which of the following positions should an object be placed so that this convex lens may act as a magnifying glass?


Describe the nature of image formed when an object is placed at a distance of 30 cm from a convex lens of focal length 15 cm.


A student did an experiment with a convex lens. He put an object at different distances 25 cm, 30 cm, 40 cm, 60 cm and 120 cm from the lens. In each case he measured the distance of the image from the lens. His results were 100 cm, 24 cm, 60 cm, 30 cm and 40 cm, respectively. Unfortunately his results are written in wrong order.

 What would be the image distance if the object distance was 90 cm?


The focal lengths of four convex lenses P, Q, R and S are 20 cm, 15 cm, 5 cm and 10 cm, respectively. The lens having the greatest power is:


Which part causes the greatest convergence?


A convex lens forms an image of an object equal to the size of the object. Draw a diagram to illustrate it.


In the following cases, where must an object be placed in front of a convex lens so that the image formed is of the same size as the object?


A student places a 8.0 cm tall object perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. He obtains a sharp image of the object on a screen placed on the other side of the lens. What will be the nature (inverted, erect, magnified, diminished) of the image he obtains on a screen? Draw ray diagram to justify your answer.


A student focussed the image of a distant object using a device ‘X’ on a white screen ‘S’ as shown in the figure. If the distance of the screen from the device is 40 cm, select the correct statement about the device.

(A) The device X is a convex lens of focal length 20 cm.

(B) The device X is a concave mirror of focal length 40 cm.

(C) The device X is a convex mirror of radius of curvature 40 cm.

(D) The device X is a convex lens of focal length 40 cm.


An object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. Find (i) the position (ii) the magnification and (iii) the nature of the image formed.


State the nature and position of the object on the principal axis to obtain a real image of the same size


Define the principal focus of a convex lens.


Define the terms principal foci and focal lengths as applied to a convex lens, and show them with the help of proper diagrams.


Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×