Physics, asked by chanduborde123, 5 months ago

A convex lens of focal length 30cm form image three times enlarged on a screen calculat distance of object distance of image and nature of image

Answers

Answered by Cosmique
66

Answer

  • Object is placed at 40 cm in front of the lens
  • Image is formed at 120 cm behind the lens
  • Nature of image: Real and inverted

Explanation

Given:-

  • The focal length of the convex lens is 30 cm  
  • An image is formed that is obtained on the screen
  • The image formed is three times enlarged

To find:-

  • Position of the object, u =?
  • Position of the image, v =?
  • Nature of image

Formulae required:-

  • The Formula for magnification of the lens

        m = v / u

  • Lens formula

       1 / f = 1 / v  -  1 / u

[ Where m is magnification, f is focal length, v is the position of image and u is the position of object ]

Solution:-

The focal length of a convex lens is always positive, so

  • the focal length of the convex lens, f = 30 cm

Since image formed is obtained on screen it means image formed is real. so the magnification of the lens will be negative.

  • magnification, m = -3

Let, the position of the image be v and position of the object be u

Using the formula for magnification of the lens

→ m = v / u

→ -3 = v / u

v = -3 u     ......equation (1)

Now, Using lens formula

→ 1 / f = 1 / v  -  1 / u

→ 1 / 30 = 1 / v - 1 / u

[ Using equation (1) ]

→ 1 / 30 = 1 / ( -3 u)  -  1 / u

→ 1 / 30 = ( - 1 - 3 ) / ( 3 u )

→ 1 / 30 = -4 / 3u

→ 3 u = -4 × 30

u = -40 cm

Putting value of u in equation (1)

→ v = -3 u

→ v = -3 × -40

v = 120 cm  

Hence,

  • Position of the object is 40 cm in front of the lens
  • Position of the image is 120 cm behind the lens
  • The image formed is real and inverted in nature.    

   

Answered by suhailchakraborty
0

Answer:

Answer

Object is placed at 40 cm in front of the lens

Image is formed at 120 cm behind the lens

Nature of image: Real and inverted

Explanation

Given:-

The focal length of the convex lens is 30 cm  

An image is formed that is obtained on the screen

The image formed is three times enlarged

To find:-

Position of the object, u =?

Position of the image, v =?

Nature of image

Formulae required:-

The Formula for magnification of the lens

       m = v / u

Lens formula

      1 / f = 1 / v  -  1 / u

[ Where m is magnification, f is focal length, v is the position of image and u is the position of object ]

Solution:-

The focal length of a convex lens is always positive, so

the focal length of the convex lens, f = 30 cm

Since image formed is obtained on screen it means image formed is real. so the magnification of the lens will be negative.

magnification, m = -3

Let, the position of the image be v and position of the object be u

Using the formula for magnification of the lens

→ m = v / u

→ -3 = v / u

→ v = -3 u     ......equation (1)

Now, Using lens formula

→ 1 / f = 1 / v  -  1 / u

→ 1 / 30 = 1 / v - 1 / u

[ Using equation (1) ]

→ 1 / 30 = 1 / ( -3 u)  -  1 / u

→ 1 / 30 = ( - 1 - 3 ) / ( 3 u )

→ 1 / 30 = -4 / 3u

→ 3 u = -4 × 30

→ u = -40 cm

Putting value of u in equation (1)

→ v = -3 u

→ v = -3 × -40

→ v = 120 cm  

Hence,

Position of the object is 40 cm in front of the lens

Position of the image is 120 cm behind the lens

The image formed is real and inverted in nature.    

Explanation:

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