A watch repairer examines watch using a convex lens of focal length 10.0 cm as a simple magnifying object. The lens is held close to eye and virtual image is formed at the near point (25 cm from eyes). Calculate the magnification?

2.5

No worries! We‘ve got your back. Try BYJU‘S free classes today!

1.4

No worries! We‘ve got your back. Try BYJU‘S free classes today!

3.5

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

0.4

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is C 3.5
$m = 1 + \frac{D}{f}$
$= 1 + \frac{25}{10} = 3.5$

Suggest Corrections

Similar questions

Q. A converging lens of focal length 6.25 cm is used as a magnifying glass. If near point of the observer is 25 cm from the eye and the lens is held close to the eye, then the magnification is :

The focal length of the objective and eye lens of a compound are 2 cm and 6.25 cm respectively. The distance between the lenses is 15 cm. How far the objective lens will be object be kept so as to obtain the final image at the near point of the eye. Also calculate its magnifying power.

Q. A convex lens of focal length

12.5 c m

is used as a simple microscope. When the image is formed at infinite. Magnification is ________ (Near point for the normal vision is

25 c m

)

Answer the following questions:

(a) The angle subtended at the eye by an object is equal to the angle subtended at the eye by the virtual image produced by a magnifying glass. In what sense then does a magnifying glass provide angular magnification?

(b) In viewing through a magnifying glass, one usually positions one’s eyes very close to the lens. Does angular magnification change if the eye is moved back?

(c) Magnifying power of a simple microscope is inversely proportional to the focal length of the lens. What then stops us from using a convex lens of smaller and smaller focal length and achieving greater and greater magnifying power?

(d) Why must both the objective and the eyepiece of a compound microscope have short focal lengths?

(e) When viewing through a compound microscope, our eyes should be positioned not on the eyepiece but a short distance away from it for best viewing. Why? How much should be that short distance between the eye and eyepiece?

Q. A compound microscope consists of two convex lenses of focal length

2

cm and

5

cm. When an object is kept at a distance of

2.1

cm from the objective, a virtual and magnified image is formed

25

cm from the eye piece. Calculate the magnifying power of the microscope.

Join BYJU'S Learning Program

A watch repairer examines watch using a convex lens of focal length 10.0 cm as a simple magnifying object. The lens is held close to eye and virtual image is formed at the near point (25 cm from eyes). Calculate the magnification?

The correct option is C 3.5m=1+Df =1+2510=3.5

The correct option is C 3.5
$m = 1 + \frac{D}{f}$
$= 1 + \frac{25}{10} = 3.5$