List four precautions that a student should observe while determining the focal length of a given convex lens by obtaining an image of a distant object on a screen.

Open in App

Solution

Focal length
Focal length is the distance between the optical centre of a lens to its focus.
The focal length of a lens is describe by the form, $\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$ , where, v and u are the image distance and object distance respectively, and f is the focal length.
List of precautions
The lens and screen should be at the same level.
The image of the wall should be clear and suitable for image production.
A meter scale has to be used to measure the focal length and image distance.
To avoid parallax error in meter-scale one has to take the reading of the meter scale perpendicularly.
Distance should be measured only when a fine structural sharp image of the distant object is produced.

Suggest Corrections

Similar questions

Q. A student has obtained an image of a distant object on a screen to determine the focal length

F_{1}

of the given lens. His teacher after checking the image, gave him another lens of focal length

F_{2}

and asked to focus the same object on the same screen. The student found that to obtain a sharp image he has to move the lens away from the screen. From this finding we may conclude that both the lenses given to the student were :

Q. Given below are few steps followed in the determination of focal length of a given convex lens by obtaining a sharp image of a distant object :
a) measuring distance b/w lens and screen
b) adjust the position of lens to form a sharp image
c) select a suitable distant object
d) hold the lens b/w the object and the screen withits faces parallel to the screen .
Write the correct sequence of steps for determining focal length .

in order to determine the focal length of a convex lens by obtaining the image of a distant object on a screen , the position of the screen should be :

a)perpendicular to the plane of convex lens

b)parallel to the plane of convex lens

c)inclined at an angle of 30degree from plane of lens

d)anywhere in any direction

Q. A sharp image of a distant object is obtained on a screen using a convex lens. In order
to determine the focal length of a lens, a student needs to measure the distance between:

A student has obtained a highly diminished image of the Sun on a screen using a convex lens. In order to determine the focal length of the lens, what should he measure?

Join BYJU'S Learning Program