Advertisements
Advertisements
प्रश्न
An object of height 4.0 cm is placed at a distance of 30 cm from the optical centre 'O' of a convex lens of focal length 20 cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre 'O' and principal focus 'F' on the diagram. Also find the approximate ratio of size of the image to the size of the object.
उत्तर
Given that ,
u = -30 cm
f = 20 cm
v = ?
Using lens formula, we get
`1/f = 1/v - 1/u`
`=> 1/20 = 1/v - 1/(-30)`
`=> 1/v = (3-2)/60`
=> v = 60 cm
So the image will be formed at a distance of 60 cm from the lens as shown in the figure given below.
Now using magnification formula we can write,
`m = v/u = h_"image"/h_"object"`
`=> 60/(-30) = h_"image"/4`
`=> h_"image"` = -8 cm
The negative sign shows that the image formed will be inverted and real. The ratio of size of the image to the size of the object is `8/4 = 2`
APPEARS IN
संबंधित प्रश्न
Draw a ray diagram to show the formation of image in the above situation
Draw a labelled ray diagram to show how a ray of light is refracted when it passes:
from an optically denser medium into air.
Where should an object be placed in front of a convex lens so as to obtain its virtual, erect and magnified image?
What is a 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.
A convex lens produces an inverted image magnified three times of an object placed at a distance of 15 cm from it. Calculate focal length of the lens.
Where must a point source of light be placed in front of a convex lens so as to obtain a parallel beam of light?
We can burn a piece of paper by focussing the sun rays by using a particular type of lens. Name the type of lens used for the above purpose. Draw a ray diagram to support your answer.
Can one bum a piece of paper in daylight by just using a convex lens instead of a match or any direct flame? Support your answer with the help of an appropriate ray diagram.
Write the name.
The lens used in simple microscope.
