Advertisements
Advertisements
प्रश्न
An illuminated object lies at a distance 1.0 m from a screen. A convex lens is used to form the image of the object on a screen placed at a distance of 75 cm from the lens. Find:
- the focal length of the lens, and
- the magnification.
Advertisements
उत्तर
Distance of object from screen = 1.0 m = 100 cm
v = 75 cm,
u = 100 – 75 = 25 cm = -25 cm
(i) f = ?
`1/"f" = 1/"v" -1/"u"`
= `1/75 - (1/-25)`
= `1/75 + 1/25`
`1/"f" = (1 + 3)/75 = 4/75`
f = `75/4`
f = 18.75
(ii) Magnification (m) = `v/u = 75/-25 = -3`
Magnification (m) = 3
The -ve symbol indicates that the created image is actual and inverted.
APPEARS IN
संबंधित प्रश्न
The following diagram shows an object AB and a converging lens L with foci F1 and F2. Draw two rays from the object AB and complete the diagram to locate the position of the image CD. Also mark on the diagram the position of eye from where the image can be viewed.
The following diagram shows an object AB and a converging lens L with foci F1 and F2 State three characteristics of the image in relation to the object.
Where is the object placed with respect to the principal focus of a magnifying glass, so as to see its enlarged image? Where is the image obtained?
Ray diagram for the formation of image by a magnifying glass.
The magnification by a lens is +0.5. Name the lens and state how are u and v related?
Name the lens used as a magnifying glass.
What information we seek by the linear magnification of the image when it is positive or negative?
Copy and complete the following ray diagram.
An erect, magnified, and a virtual image is formed when an object is placed between the optical centre and principal focus of a lens.
(i) Name the lens.
(ii) Draw a ray diagram to show the formation of the image with the above-stated characteristics.
An object AB is placed between 2F1 and F1 on the principal axis of a convex lens as shown in the diagram. Copy the diagram and using three rays starting from point A, obtain the image of the object formed by the lens.
