Advertisements
Advertisements
प्रश्न
An erect image 2.0 cm high is formed 12 cm from a lens, the object being 0.5 cm high. Find the focal length of the lens.
उत्तर
Given:
Image distance, v =-12 cm (Image is erect.)
Height of the object, h = 0.5 cm
Height of the image, h' = 2.0 cm
Applying magnification formula, we get:
m = v/u = h'/h
-12/u = 2.0/0.5
or, object distance, u =-3 cm
Applying lens formula, we get:
1/v- 1/u = 1/f
1/(-12)-1/(-3) = 1/f
or, 1/f = 3/12
or, focal length, f = 4.0 cm
APPEARS IN
संबंधित प्रश्न
The height of the image formed by an object of height 10 cm placed in front of a plane mirror is __________.
(a) 5 cm
(b) 10 cm
(c) 15 cm
(d) 20 cm
Give two circumstances in which a concave mirror can form a magnified image of an object placed in front of it. Illustrate your answer by drawing labelled ray diagrams for both.
A virtual, erect and magnified image of an object is to be produced with a concave mirror of focal length 12 cm. Which of the following object distance should be chosen for this purpose?
(i) 10 cm
(ii) 15 cm
(iii) 20 cm
Give reason for your choi
What sign (+ve or −ve) has been given to the following on the basis of Cartesian Sigh Convention?
Height of a virtual image.
What is the ratio of the height of an image to the height of an object known as?
Write down the magnification formula for a lens in terms of object distance and image distance. How does this magnification formula for a lens differ from the corresponding formula for a mirror?
To obtain a magnification of, –0.5 with a convex lens, the object should be placed:
(a) at F
(b) between optical centre and F
(c) between F and 2F
(d) beyond 2F
A magnifying lens has a focal length of 100 mm. An object whose size is 16 mm is placed at some distance from the lens so that an image is formed at a distance of 25 cm in front of the lens.
What is the distance between the object and the lens?
A magnifying lens has a focal length of 100 mm. An object whose size is 16 mm is placed at some distance from the lens so that an image is formed at a distance of 25 cm in front of the lens.
Where should the object be placed if the image is to form at infinity?
What do you mean by linear magnification?
